.  1  _-..--_-_ 


REESE   LIBRARY 

:'  i  I  K 

UNIVERSITY  OF  CALIFORNIA 


,  «s  No. 


Accessions 

v    u    u--i 


NATURAL    ASPHALT 


TWENTY  YEARS'  PRACTICAL  EXPERIENCE 


OF 


NATURAL   ASPHALT 


AND 


MINERAL  BITUMEN 


BY 

W.   H.  DELANO 

r  1 
ASSOC.  INST.  C.E. 

GENERAL   MANAGER  OF  THE   COMPAGNIE   G^NlSRALE   DBS  ASPHALTES    DE 
FRANCE  LIMITED 


E.  &   F.  N.  SPON,   125   STRAND 
Jlefo  gorfe: 

SPON   &  CHAMBERLAIN,    12  CORTLANDT   STREET 
1893 


v 


PREFACE. 


IN  the  year  1880  the  author  read  a  paper  at 
the  Institution  of  Civil  Engineers,  London,  on 
Asphalt,  which  was  reprinted  in  Van  Nostrand's 
'Engineering  Magazine,'  New  York,  December 
1880,  and  January  1 88 1. 

Since  that  periodnfte  use ,  of  asphalt  (also,  un- 
fortunately, of  its  various  imitations)  has  greatly 
extended  indeed  in  all  parts  of  the  civilized  world, 
so  that  a  popular  exposition  of  its  qualities,  uses, 
and  abuses,  has  become  a  desideratum. 

The  author  has  to  express  his  thanks  to  various 
directors  and  managers  in  London,  New  York, 
Berlin,  Vienna,  Brussels,  Rome,  Turin,  Amsterdam, 
and  above  all  to  the  Municipal  and  Government 
Engineers  of  Paris,  for  much  information. 

117  QUAI  VALMY,  PARIS. 


CONTENTS. 


PART  I. 

NOMENCLATURE   OF   ASPHALT   AND    ITS    COMBINATIONS. 

PAGE 

ASPHALT  ROCK ..  2 

ASPHALT  MASTIC 3 

GRITTED  ASPHALT  MASTIC       4 

BITUMEN 4 

BUTUMINOUS  CONCRETE     o 

GEOLOGY  OF  ASPHALT        6 

ANALYSIS  OF  ASPHALT       4 

LIST  OF  ASPHALT  MINES 19 

PART  II. 

USES   OF   ASPHALT. 

ITS  QUALITIES       12 

FIRE-  AND  VERMIN-PROOF  FLOORS 15 

COATINGS  FOR  ARCHES  OF  BRIDGES,  VIADUCTS,  ETC.     ..  15 

CASEMATES     is 

RESISTANCE  TO  ACIDS 18 

INSULATION 19 

POWDER  MAGAZINES 19 

VIBRATION-ABSORBENT        19 

ROADWAYS      23 

DURABILITY 26 

MALLEABILITY       , 28 

NON-INJURY  BY  HEAT  OR  FROST 29 

NOISELESSNESS         3O 

AGORAPHOBIA  :  NERVOUS  AFFECTION  CAUSED  BY  STREET 

NOISE 13 

ASPHALT  ROADWAYS  IN  PARIS        32 

WOOD  PAVEMENT         32 

TRACTION  ON  ASPHALT  ROADWAYS       36 


viii  ASPHALT. 

PART  III. 

MODES   OF   APPLYING  ASPHALT. 

PAGE 

ROADWAYS:  CAMBER 37 

,,  SUBSOIL 41 

.,  CONCRETE      41 

,,  TIME  OF  LAYING 43 

,,  HOT  ASPHALT  POWDEK     43 

FOOT-PATHS  OF  COMPRESSED  ASPHALT 45 

,,  GRITTED  ASPHALT  MASTIC        45 

COATINGS  FOR  MASONRY 52 

CASEMATES 52 

ROOFS      52 

SILOES     53 

VERTICAL  APPLICATIONS     53 

INSULATION  OF  ELECTIC  WIRES      55 

ASPHALT  FLAGS  AND  SLABS     57 

PART  IV. 

GENERAL   OBSERVATIONS. 

WIDTH  OF  TIRES  FOR  HEAVY  TRAFFIC        58 

USE  OF  SALT  FOR  MELTING  SNOW        ..  58 

KERBS      59 

SPEED  OF  STREET-TRAFFIC        59 

TRAMCAR  RAILS 60 

MAINTENANCE  CONTRACTS        60 

CONVERSION  OF  OLD  ROADS  INTO  ASPHALT  ROADS  ..      ..  60 

CAUTION  MONEY  AND  MODE  OF  PAYMENT 61 

MAINTENANCE       62 

Low  PRICES 65 

IMITATIONS  OF  NATURAL  ASPHALT        66 

TRAFFIC  OF  PARIS       69. 

WEAR  OF  MACADAMISED  ROADS      70 

WORK  DONE  BY  PARISHES  WITHOUT  CONTRACTORS..      ..  71 

COST  OF  WORK  IN  PARIS 72 


TWENTY  YEARS'  PRACTICAL  EXPERIENCE 

OF 

NATURAL     ASPHALT 

AND  MINERAL  BITUMEN. 
PART    I. 

NOMENCLATURE  OF  ASPHAL7  AND  ITS 
COMBINA  TIONS. 

FOR  all  that  concerns  the  origin  of  asphalt,  its 
nature,  history  and  geological  formation,  and 
mode  of  extraction,  the  well-known  work  *  of 
M.  Leon  Malo  (who  for  thirty  years  has  been 
the  prophet  of  natural  asphalt)  is  the  best  guide. 
Of  this  gentleman  the  author  is  an  earnest  and 
grateful  disciple. 

Nomenclature. — Asphalt  is  a  natural  product 
(see  Fig.  i),  a  bituminous  limestone  in  which 
carbonate  of  lime  and  pure  mineral  bitumen  are 
most  intimately  combined  by  natural  agency,  the 
proportions  varying  from  7  per  cent,  bitumen  and 

*  '  L'  Asphalte :  son  origine,  sa  preparation,  ses  applications,  par 
Leon  Malo.'  Baudry  Si  C»e.,  £diteurs,  15  Rue  des  Saints  Peres, 
Paris. 

B 


NATURAL  ASPHALT. 


Fig.    I.— NATURAL  ASPHALT   ROCK. 


Fig.    2.— SECTION   OF   AN   ASPHALT  MINE. 

93  per  cent  carbonate  of  lime  to  20  per  cent,  bitu- 
men and  80  per  cent,  carbonate  of  lime. 


NATURAL  ASPHALT.  3 

It  is  found  in  seams  like  coal,  and  mined  in  the 
same  way  (see  Fig.  2).  Heated  on  a  hot  plate  it 
falls  to  pieces  (see  Figs.  3,  4). 


Fig.    3. — ASPHALT   ROCK    COMMINUTED   BY   HEATING  ON 
AN   IRON    PLATE — SIFTED. 


Fig.   4. — ASPHALT   ROCK   COMMINUTED   BY   HEATING  ON 
AN   IRON   PLATE — UNSIFTED. 


Asphalt  Mastic,  when  pure,  is  composed  of  asphalt 
rock  ground  to  a  fine  powder  and  mixed  hot  with 

B  2 


4  NATURAL  ASPHALT. 

a  varying  proportion  of  hot  bitumen  similar  to  that 
contained  in  the  natural  rock,  the  pasty  product 
being  run  into  moulds,  forming  the  well-known 

cakes,  which  weigh  about 
561bs.  Their  diameter  is 
30  J  inches,  and  they  are 
from  4  to  4%  inches  high. 
Analysis  should  show 
about  15  per  cent,  bitu- 
Figj  5>  men  and  85  per  cent,  of 

limestone  in  these  cakes. 

Gritted  Asphalt  Mastic  is  composed  of  pure 
asphalt  mastic,  broken  to  small  pieces  of  from  \  to 
I  inch  in  diameter,  remelted  in  a  kettle  (see  p.  50). 
There  is  added  5  per  cent,  of  pure  bitumen  and  from 
30  to  40  per  cent,  of  fine  clean  dry  grit,  the  grains 
of  the  latter  above  -|  inch  in  diameter. 

The  author  prefers  limestone  grit,  but  if  silicious 
grit  only  can  be  obtained  it  should  be  as  fine  as 
sea  sand. 

Asphaltic  or  Bituminous  Concrete  is  composed  of 
two  parts  of  hot  gritted  mastic  mixed  with  three 
parts  of  flint  pebbles,  or  rubble,  about  2\  inches 
diameter.  The  stones  should  also  be  hot. 

Bitumen  is  a  mineral  product  found  in  asphalt 
rock,  whence  it  can  be  extracted  pure.  It  is  found 
in  the  Trinidad  "Pitch  Lake,"  mixed  with  33  per 
cent,  of  fine  clay  sand  and  vegetable  matter,  and 
33  per  cent,  of  water.  It  is  also  found  in  various 


NATURAL   ASPHALT.  5 

states  of  purity,  sometimes  mixed  with  sand  or 
sulphur,  in  Auvergne  (France),  Chieti  (Italy), 
Avlona,  Selenitza  (Albania),  Beyrout,  Venezuela, 
California,  Kentucky,  Utah,  and  elsewhere,  par- 
ticularly the  Dead  Sea  (see  p.  n). 

Bitumen  is  an  exact  synonym  of  mineral  pitch  ; 
it  is  in  fact  the  Latin  equivalent  for  pitch,  and  the 
adjectival  form  "  bituminous "  has  replaced  the 
Saxon  form  "  pitchy." 

Bitumen  is  allied  to  petroleum,  naphtha  and 
shale  oils  ;  but  it  is  not  by  any  means  identical,  as 
the  results  of  their  use  show.  It  is,  as  M.  Malo 
writes,  only  "  similar  to  itself." 

The  type  and  standard  of  mineral  bitumen  is 
that  extracted  from  Seyssel  asphalt,  which  can  be 
subjected  to  500°  Fahr.,  or  x°  below  freezing  point, 
without  losing  its  tenacity,  malleability,  or  suffering 
any  deterioration. 

Its  composition  is  : — 

Carbon         85  parts. 

Hydrogen 12     ,, 

Oxygen         3     ,, 

100  parts. 

Bitumen  is  therefore  the  principal  ingredient  of 
asphalt,  but  in  that  latter  body  is  so  intimately 
intermixed  with  the  limestone  by  Nature  itself  that 
the  result — asphalt — must  be  considered  an  inde- 
pendent material,  like  granite  or  porphyry,  Roman 
cement  or  coal. 

It   may  be  imperfectly  imitated,  created  it  can 


NATURAL  ASPHALT. 


never  be.     Bitumen,  it  would  seem  from  the  testi- 
mony of    the    Seyssel    asphalt    mines,    may   have 


Fig.   6. — PROBABLE   FORMATION   OF  ASPHALT. 
AFTER   RIVER-EROSION. 

permeated,  whilst  in  a  state  of  vapour,  the  limestone, 
which   at  that  period  must    have  been    soft    (see 


NATURAL   ASPHALT. 


hypothesis  below).     Only   the  perfervent  heat  of 
Nature  can  have  vaporised  carbon. 


Fig.    7. — PROBABLE   FORMATION   OF  ASPHALT. 
BEFORE   RIVER-EROSION. 

Asphalt  is  generally  found  in  6  to  lO-feet  seams, 
between  two  layers  of  white  hard  limestone,  either 


8  NATURAL  ASPHALT. 

totally  unimpregnated  with  bitumen  or  else  with 
mere  traces  of  it,  which  have  the  appearance  of 
thin  smoke  or  the  faint  stains  in  white  marble. 
Sometimes,  however,  layers  of  sand  and  marl  are 
found,  which  must  be  propped,  or  held  up  by 
rubble. 

Some  contractors  (outside  Europe)  have  quite 
recently  used  the  term  asphalt  and  bitumen  as 
though  they  were  synonymous  and  interchange- 
able, and  even  such  an  anomalous  phrase  as  the 
following  has  been  seen  in  print : — "  Asphalt  from 
the  Trinidad  Pitch  Lake."  Such  misuse  of  terms 
should  be  strictly  avoided  in  estimates  and  speci- 
fications, as  causing  confusion. 

Bitumen  and  mineral  pitch  are  interchangeable 
terms,  but  asphalt  stands  alone. 

The  necessity  for  a  clear  and  precise  nomencla- 
ture is  shown  by  the  interesting  '  Report  on  the 
Geology  of  Trinidad/  by  G.  P.  Wall  and  J.  G. 
Sawkins,  F.G.S.,*  where  the  words — 


Asphaltum, 
Asphalt, 
Bitumen,  and 
Pitch 


are  used  to  express  one  and  the  same  aiticle, 
viz.  Trinidad  Pitch. 


There  seems  some  tendency  in  the  best  human 
nature  to  abuse  synonyms  and  revel  in  tautology. 

Sometimes  from  bad  habit,  sometimes  from 
fraudulent  motives,  gas-tar,  Stockholm  tar,  petro- 
leum and  naphtha  residuum,  shale  grease,  hard 

*  Longmans,  London. 


NATURAL   ASPHALT.  9 

pitch  from  the  distillation  of  animal  fat,  are  called 
asphalt.  This  misappropriation  of  terms,  this 
"calling  evil  good,"  should  be  sternly  reprobated 
by  engineers,  architects  and  chemists  who  cherish 
clearness  of  expression  and  detest  puzzledom. 

Analysis  of  Asphalt  (Natural  product). — As 
mined,  the  rock  should  be  of  a  chocolate  colour,  fine 
in  grain,  evenly  impregnated  with  bitumen,  free 
from  sulphur,  pyrites,  clay,  sand  or  other  extraneous 
matter.  When  examining  with  the  microscope, 
always  look  at  a  fresh  fracture. 

Rich  Val  de  Travers  rock,  containing  say  1 1  to  1 3 
per  cent,  bitumen,  should  be  mixed  with  one-half 
of  fine  Seyssel  rock  containing  7  per  cent,  of  bitu- 
men, which  is  fixed  and  invariable,  producing  thus 

— —  =  9   per  cent,  powder,  suitable   for   a 

climate  like  that  of  London. 

The  same  may  be  done  with  Ragusa  (Sicilian 
rock),  which  is  rich  in  bitumen  of  excellent  quality, 
only  the  texture  or  grain  of  the  limestone  is  loose, 
whereas  that  of  Seyssel  is  fine  and  dense. 

Mons  and  St.  Jean  de  Marvejols  asphalts  are 
similar  in  structure  to  Ragusa,  but  the  limestone  is 
much  finer. 

The  rough  and  ready  way  ol  testing  asphalt  is 
to  dissolve  its  powder  taken  from  a  three-ton 
bulk,  in  carbon  bisulphide,  turpentine,  or  ether. 
Stir  well  with  a  glass  rod  and  strain  through  a 
thick  paper  filter  ;  then  let  the  sulphide  evaporate, 


CKIVEBSITT 


10  NATURAL   ASPHALT. 

which  it  will  do  at  70°  ;  weigh  the  bitumen  and 
the  residuum,  afterwards  washing  the  latter  in 
hydrochloric  acid,  which  will  cause  the  lime  to 
effervesce,  leaving  any  silica,  pyrites,  &c.  ;  but  for 
an  absolute  test  an  analyst  accustomed  to  hydro- 
carbons should  be  called  in. 

The  same  test  does  for  bitumen,  to  ascertain 
the  proportion  of  clay  or  other  impurities  in  it  ; 
naturally  the  practical  test  for  a  new  asphalt  is  to 
lay  it  in  a  crowded  thoroughfare  and  let  three 
winters  and  summers  pass  over  it. 

Refined  Trinidad  Pitch  will  always  contain 
from  20  to  25  per  cent,  of  fine  clay  ;  nevertheless  it 
is  so  tough,  malleable  and  stringy,  that  for  asphalt 
mastic  it  is  preferable  to  some  other  short  fibred 
bitumens  chemically  purer. 

List  of  Asphalt  Mines.— Asphalt  is  found  near 
Seyssel,  France,  in  the  Rhone  Valley  between  the 
towns  of  Bellegarde  and  Seyssel,  the  centre  of  the 
concession  being  the  railway  station  of  Pyrimont, 
specially  created  for  the  important  mastic  works  of 
the  Compagnie  Generale  des  Asphaltes  de  France, 
of  1 17  Quai  de  Valmy,  Paris  ;  at  Travers,  belonging 
to  the  canton  of  Neufchatel,  Switzerland,  conceded 
till  1907  to  an  English  company  in  London  ; 
Mons  and  St.  Jean  de  Marvejols,  near  Alais, 
France ;  Chieti,  in  the  Abruzzi,  Italy ;  Ragusa, 
Sicily ;  Auvergne  (though  here  mostly  bitu- 
minous sandstone)  ;  Lobsann  in  Alsace  (much 


NATURAL  ASPHALT.  II 

mixed  with  iron  pyrites)  ;  Limmer,  near  Hanover, 
Germany.  Sandstone  impregnated  with  bitumen 
is  found  in  Kentucky,  Utah,  California,  and  at 
Maestu  in  Spain. 

The  chief  source  of  supply  of  mineral  bitumen 
is  the  British  island  of  Trinidad,  West  Indies,  but 
there  are  also  supplies  to  be  had  from  Chieti, 
Italy ;  Auvergne,  Vallona,  Albania ;  Bermudez 
in  Venezuela ;  Barraquilla  in  Columbia,  Central 
America  ;  Province  of  Oran,  Algeria';  *  Beyrout, 
Syria,  &c.  The  bitumen  from  the  Dead  Sea  is 
only  used  for  medium  or  black  varnish;  the  supply 
is  scanty. 

Bitumen  to  be  good  should  be  free  from  dross, 
non-evaporative  and  contain  no  oils  that  will  evapo- 
rate at  480°  Fahr. ;  be  perfectly  black,  not  brilliant, 
and  at  70°  Fahr.  have  the  consistency  of  bees'-wax. 
The  best  way  to  test  the  quality  is  to  draw  it  out 
in  threads  ;  the  longer  they  stretch  the  better  the 
sample. 

*  The  author  saw,  some  ten  years  ago,  in  Algeria,  an  Arab 
sheikh,  on  the  borders  of  the  Chelif  River,  who  was  pitching  his 
shallow  flat-bottomed  boat  with  pitch  from  a  scanty  bituminous 
spring  near,  and  was  reminded  of  the  divine  command  to  the 
Patriarch  Noah — "  Bituminabis  earn  bitumine"  says  the  Vulgate. 


12  NATURAL   ASPHALT. 


PART    II. 

THE    USES  OF  ASPHALT. 

BEFORE  describing,  from  long  and  varied  ex- 
perience, the  best  modes  of  using  asphalt,  the 
author  would  express  his  firm  belief  that  this 
valuable  and  unique  material  was  specially  created 
for  certain  ends,  like  coal,  iron,  copper,  &c.  It  is 
for  man  to  study  and  utilise  the  gift. 

Its  Qualities. — After  the  necessary  manipulation, 
it  becomes  impervious  to  water  and  air,  resists  fire 
and  acids,  insulates  the  electric  circuit,  produces  no 
sparks  by  contact  with  iron,  repels  vermin,  absorbs 
vibration  ;  its  vapours  are  antiseptic  ;  it  is  durable, 
easily  repaired  ;  so  malleable  that  it  can  be  applied 
to  any  curve,  so  ductile  that  it  will  yield  to  any 
ordinary  pressure  from  whatever  direction  without 
cracking.  It  is  unaffected  by  frost,  and  though 
slightly  softened  by  heat,  say  125°  Fahr.,  it  never 
disintegrates,  even  at  450°,  and  upon  returning 
to  its  normal  temperature  has  lost  none  of  its 
qualities. 

It  produces  no  dust,  consequently  no  mud. 

It  can  be  laid  by  workmen  of  ordinary  intel- 
ligence in  any  climate,  for  its  malleability  can  be 


NATURAL  ASPHALT.  13 

increased  or  decreased  at  will,  so  as  to  suit  the 
temperature  of  arctic  or  of  tropical  regions. 

Apart  from  its  hygienic  properties,  its  noiseless- 
ness,  its  harmonious  tint,  it  is  most  agreeable'  to 
walk  upon  (not  hard  and  slippery,  like  granite, 
cement,  tiles,  &c.).  It  is  in  fact  the  street  carpet. 

Its  duration  is  greater  than  that  of  granite  and 
flag,  its  first  cost  and  annual  maintenance  less. 

Illilllllfilli 


Fig.  8. 

The  traction  for  horses  on  the  level  is  easy,  they 
can  draw  from  three  to  six  times  as  much  as  on 
rough  coarse  metal  or  stone  pitched  roads. 

Imperviousness  to  Moisture. — Let  us  consider  the 
"  damp  course"  (Fig.  8),  so  simple,  and  so  useful, 
that  it  ought  to  be  made  compulsory  in  building 
operations. 


14  NATURAL   ASPHALT. 

When  it  is  remembered  that  one  porous  brick,  8^ 
inches  by  4J-  inches  by  i£  inches,  weighing  say  4*  78 
Ibs.  avoirdupois,  will  absorb  and  hold  £  Ib.  of 
water,  one  is  astounded  at  the  amount  of  water 
there  may  be  contained  in  an  ordinary  wall,  drawn 
up  by  capillarity,  causing  rheumatism,  fever,  and 
other  diseases,  apart  from  discomfort  and  depres- 
sion, shortening  the  lives  of  adults,  checking  the 


Fig.  9. 

development  of  children.  Asphalt  arrests  capillarity, 
and  settlement  of  masonry  does  not  cause  it  to 
crack  like  cement. 

Some  twenty-five  years  ago,  a  handsome  house 
was  built  on  the  borders  of  the  Lake  of  Enghien, 
a  Seyssel  asphalt  damp  course  was  used,  and  the 
walls,  as  far  as  regards  the  unceasing  action  of 
capillarity,  kept  perfectly  dry.  But  one  day  some 


NATURAL  ASPHALT.  15 

underpinning  was  done  ;  the  mason  forgot  to  relay 
the  asphalt  damp  course,  or  else  thought  it  was  a 
fad  and  wilfully  neglected  to  repair  it ;  the  conse- 
quence was,  walls  saturated  to  such  an  extent,  that 
the  house  became  uninhabitable. 

Fire-  and  Vermin-proof  Floors. — An  excellent 
and  springy  floor  is  made  by  setting  the  joists  in 
asphalt  mastic,  and  afterwards  nailing  down  the 
battens  in  various  patterns,  care  being  taken  not 
to  leave  sufficient  space  between  the  battens  and 
asphalt  for  rats  and  mice  to  pass  ;  the  asphalt  is  un- 
inflammable, and  will  not  allow  air  to  pass  (Fig.  9). 

Sometimes  the  boards  or  battens  are  laid  direct 
on  asphalt  without  joists,  but  then  the  floor  is  not 
so  elastic,  and  may  not  always  keep  level. 

Coatings  of  Asphalt  Mastic  upon  the  Arches  of 
Viaducts  and  Bridges  of  Stone  or  Iron  keep  out 
moisture  from  above,  and  so  prevent  the  action  of 
percolation  and  frost  upon  the  joints  and  key- 
stones, and  thus  arrest  decay.  (Figs.  10  and  n.) 

Water  is  the  enemy  and  must  be  kept  out — well 
laid  asphalt  is  the  remedy.  How  many  accidents 
are  constantly  occurring  to  railway  bridges,  owing 
to  the  neglect  of  so  simple  a  precaution. 

Casemates  should  always  be  coated  with  liquid 
asphalt  under  the  bomb-proof  earth  covering  (see 
Fig.  12). 

In  time  of  war  soldiers  must  live  in  dry  case- 
mates or  they  will  soon  be  down  on  the  sick-list. 


i6 


NATURAL  ASPHALT.  I? 

Military  engineers   are  expensive,  and  it  pays   to 
take  care  of  them. 

Heavy  masonry  always  settles,  and  if  only  a 
Portland  cement  coating  be  used  it  will  crack  and 
split,  and  be  of  no  more  use  to  keep  water  off  than 
a  sieve. 


Fig.   12. 

The  author  once  witnessed  the  following  proof  of 
the  correctness  of  this.  About  20  feet  of  earth  was 
removed  from  the  roof  of  a  bomb-proof  casemate, 
and  the  coating  of  Seyssel  asphalt  examined,  after 
40  years'  burial.  There  was  no  crack  anywhere,  it 
had  yielded  to  the  settlement  of  the  masonry,  long 
roots  of  lucerne  had  in  vain  tried  to  penetrate  it. 
The  interior  of  the  casemate  was  dry  and  habitable. 

The  strong  room  of  an  important  Public 
Company  in  Paris  has  been  walled  with  bitu- 

C 


i8 


NATURAL  ASPHALT. 


minous  concrete,  the  walls,  with  books  inside, 
having  been  previously  submitted  to  a  fierce  fire. 
It  is  as  impenetrable  to  air  as  to  water. 

When  a  coating  of  gritted  asphalt  is  used  on  a 
roof,  it  will,  in  case  the  foundations  are  burnt,  fall 
in  and  stifle  the  flames  like  a  wet  blanket. 

The  result  has  been  proved  by  insurance 
companies  on  several  occasions,*  by  actual  tests. — 
It  is  flame-proof. 


Fig.    13. — CONDUIT  FOR  ELECTRIC  WIRES. 

Resistance  to  Acids. — Specially-made  mastic  will 
resist  the  action  of  acids  for  a  long  time  ;  the 
bitumen  resists  completely  and  defends  the  lime- 

*  See  *  Note  sur  1'application  de  1'asphalte  coule  sur  les  planchers 
des  Magasins  et  Greniers  pour  empecher  la  propagation  de 
1'incendie.  Imprimerie  E.  Capiomont  et  Cie,  6  Rue  des  Poitevins, 
Paris,  1888.' 


NATURAL  ASPHALT.  19 

stone   component.      It    is    used    for   lining   tanks 
required  in  electrolysis  and  for  electric  batteries. 

Insulation. — Bitumen  is  an  excellent  insulator 
for  electric  wires,  at  least  30  per  cent,  superior  to 
gas-tar.  It  will  resist  the  action  of  underground 
moisture. 

The  author  has  often  seen  leakages  of 
electricity  completely  arrested  by  drowning  the 
wires  in  asphalt  mastic  as  they  lay.  This  was 
particularly  the  case  at  the  National  Opera  House 
in  Paris,  where  condensed  water,  getting  into  the 
trough  where  the  wires  were,  rotted  the  hempen 
coating  and  caused  a  leakage  of  30  per  cent. 

Powder  Magazines. — Asphalt  produces  no  sparks 
by  contact  with  steel,  so  is  excellent  for  powder 
magazines.  The  floors,  often  made  with  timber 
fastened  with  copper  nails,  rot  after  a  time,  but 
asphalt  defies  time.  Of  course,  for  powder 
magazines  pure  compressed  or  pure  liquid  mastic 
should  be  used,  not  gritted  mastic. 

Absorption  of  Vibration  by  Bituminous  or 
Asphaltic  Concrete  and  Compressed  Asphalt  Powder 
in  Moulds. — One  of  the  most  interesting  applica- 
tions of  asphalt  is  that  of  bituminous  or  asphaltic 
concrete  for  quick-speeded  machinery,  such  as  dy- 
namos and  their  motors,  grinding  machinery  like 
Carr's  disintegrator  (700  revolutions  per  minute) 

C  2 


20  NATURAL  ASPHALT. 

hydro-extractors  (1400  revolutions  per  minute), 
printing-machines,  and  percussive  machines  like 
gas  -  engines,  stamping-presses,  steam  -  hammers, 
spring-hammers,  &c. 

The  author  has  during  the  last  twenty  years 
arrested  many  a  lawsuit  begun  by  indignant  neigh- 
bours against  users  of  machinery  in  the  crowded 
houses  of  cities.  A  high-speed  engine  working  in 
a  cellar  will  make  a  seven-story  house  tremble,  and 
at  night  prevent  sleep  of  the  inmates. 

The  asphalt  concrete  may  be  run  in  moulds  to 
any  shape  and  sold  by  the  cube. 

The  cure  is  complete,  when  the  mass  is  big 
enough.  For  instance,  take  the  foundations  for 
a  stamping-press,  the  gradual  annihilation  of  the 
concussion  can  be  felt  by  placing  the  hand  on  the 
side  of  the  block  of  bituminous  concrete  which 
receives  it.  The  latest  application  of  asphalt  con- 
crete for  this  purpose  is  that  of  the  electric-light 
motors  at  Moe't  and  Chan  don's,  Epernay,  France, 
where  it  was  absolutely  necessary  to  prevent  the 
8,000,000  bottles  of  champagne  in  the  cellars  from 
shaking. 

The  foundations  for  the  dynamos  and  their 
motors  in  most  of  the  Paris  theatres  are  of  bitu- 
minous concrete.  They  are  surrounded  by  brick 
walls.  No  vibration  is  felt ;  the  temperature  in 
the  cellars  where  the  engines  are  is  120°  Fahr. 

For  steam-engines  the  surface  of  the  foundation 
must  be  laid  in  cement,  or  have  a  layer  of  stone,  to 
avoid  bad  effects  of  oil  and  grease,  which  are  pre- 


Fig.  14. 


22  NATURAL  ASPHALT. 

judicial  to  asphalt  after  a  certain  time.  This 
application  of  asphalt  requires  extra  care,  and 
must  not  be  attempted  except  by  professional 
asphalters,  as  a  failure  would  be  no  trifling  matter. 
Only  the  best  materials  must  be  used.  A  block 
may  take  three  days  or  more  to  settle  and  cool. 

The  same  effect  can  be  obtained  by  successive 
layers  of  hot  asphalt  powder  compressed  in  a 
strong  steel  frame  ;  and  this  plan  is  used  for  steam 
hammers,  avoiding  the  jarring  of  walls  and  the 
breakage  of  glass  in  skylights,  &c. 

M.  Malo  was  the  first  to  use  asphalt  to  avoid 
the  vibration  of  machinery,  and  has  carried  out  at 
Pyrimont  Works,  the  centre  of  the  Seyssel  Asphalt 
Concession,  many  ingenious  applications.  The 
author  has  followed  his  lead  in  Paris.  The 
instances  are  now  too  numerous  to  detail  ;  they 
vary  from  stamping-presses  and  printing-machines 
to  the  heaviest  engines. 

At  the  present  time  (1893)  an  underground  rail- 
way is  being  constructed  near  the  astronomical 
observatory  of  Paris.  The  astronomers  find  that 
their  mercury  bath  and  various  delicate  instruments 
vibrate.  Both  M.  Malo  and  the  author  are  being 
consulted  as  to  the  remedy,  which  will  have  to 
be  paid  for  by  the  railway  company. 

Either  the  instruments  will  have  to  be  mounted  on 
bituminous  concrete  foundations,  or  else  the  whole 
building  of  the  observatory  be  insulated  by  a  wall 
of  bituminous  concrete  at  considerable  expense. 

Many  useful  new  applications  of  asphalt  concrete 


NATURAL  ASPHALT.  23 

are  yet  in  their  infancy.  One  is  to  line  the  granite 
embrasures  efforts  with  this  material,  which  makes 
no  splinters.  Splinters  often  do  more  harm  to 
artillerymen  than  explosive  bullets.  Leaden  bullets 
will  flatten  when  fired  against  asphalt  powder 
heaped  up. 

It  is  this  quality,  shared  by  indiarubber,  cork, 
and  to  a  certain  extent  wood,  which,  coupled 
with  its  impermeability  ai«d  artistic  colour,  renders 
compressed  asphalt  so  suitable  for  the  streets  of 
crowded  cities. 

The  din  and  jar  of  street  traffic  are  a  torment  to 
artists,  literary  men,  men  of  business,  women  and 
young  children. 

The  passing  at  8  miles  an  hour  of  a  heavily 
laden  four-wheel  van  over  a  stone  or  cobble 
roadway,  will  make  a  six-story  house  tremble 
from  top  to  bottom,  and  often  dislodges  bricks,  tiles, 
and  architectural  ornaments. 

It  is  fortunate  for  dwellers  in  cities  that  there 
exists  in  compressed  asphalt  a  pavement,  cheaper 
than  granite,  that  suppresses  such  exasperating 
annoyance. 

Asphalt  roadways  enhance  the  value  of  house 
property,  diminish  traction,  are  not  of  themselves 
slippery ;  produce  no  dust,  therefore  no  mud ; 
absorb  no  liquid  nor  solid  excremental  matter, 
nor  filth  nor  putridity,  therefore  under  the  hot  blaze 
of  a  summer  sun  emit  no  miasmata.  Asphalt 
affords  no  element  for  fermentation,  is  therefore 
hygienic  par  excellence. 


24  NATURAL  ASPHALT. 

It  should  be  used  universally ;  the  only  excuse 
admissible  for  its  non-use  should  be  the  want  of 
money  and  the  power  to  borrow  it.  But  there  are 
always  enemies  to  progress — those  who  say,  What 
was  good  enough  in  old  times  is  good  enough 
now ;  those  who  ignore  the  results  of  comparative 
experiment ;  the  faddists  ;  and  those  who  condemn 
without  examination. 

Now  what  are  the  disadvantages  of  asphalt  ? 
The  wise  man  who  has  to  judge  a  new  material  or 
process  may  make  two  columns  on  a  sheet  of  paper, 
inscribe  in  the  one  the  advantages,  in  the  other 
the  disadvantages ;  the  balance  is  one  side  or 
the  other — then  he  knows  what  course  to  pursue. 

Now  a  smooth  pavement  is  unsuitable  to  horses 
with  a  load  to  drag.  There  is  no  grip,  and  it 
may  be  laid  down  that,  in  almost  all  circumstances, 
3  in  100  is  the  maximum  gradient  for  compressed 
asphalt  roads. 

Again,  in  the  temperate  zone  there  will  be  some 
days  in  the  year  when  it  drizzles.  Then  the  fine 
dust  lying  on  the  asphalt  is  at  once  converted 
into  a  thin  pellicle  of  sticky  mud,  which  may  cause 
horses  to  slip  unless  well  held  up  by  their  drivers  ; 
a  heavy  rain  does  no  harm,  indeed  it  does  good  by 
washing  the  surface. 

In  Paris,  where  compressed  asphalt  was  first 
used,  there  are  bins  in  the  foot-paths  or  side-walks- 
containing  stores  of  fine  red  sand. 

The  scavengers  at  once  sprinkle  the  asphalt 
surface ;  the  men  use  a  wheelbarrow  and 


NATURAL  ASPHALT.  2$ 

shovel,  giving  the  latter  a  smart  twist  at  the 
moment  of  throwing,  which  scatters  the  sand 
uniformly,  and  slipping  is  prevented  ;  but  the  better 
plan,  which  is  also  used  in  Paris,  is  to  screw  the 
hose  on  to  the  street  hydrant  and  flush  the  surface, 
afterwards  using  the  squeegee. 

When  a  horse  falls  on  asphalt  he  does  not 
break  his  knees  as  he  would  on  stone  setts  or 
macadam. 

Some  sand,  ashes  or  cinders  thrown  will  facilitate 
his  rising,  or  a  cloth  thrown  under  his  fore  legs. 

Horses  get  accustomed  to  asphalt,  and  must 
like  it,  at  any  rate  340  days  out  of  the  365,  as  the 
traction  is  so  much  easier  than  on  stone,  macadam, 
or  wood. 

It  is  quite  clear  that  when  improved  roadways 
are  made,  there  must  be  provided  also  improved 
modes  of  cleansing  them. 

Compressed  asphalt  must  be  kept  clean  from 
horse-dung  and  other  impurities,  and  be  flushed 
once  at  least  in  24  hours,  either  by  hose  and  hydrant 
or  by  water  cart,  and  then  squeegeed. 

In  big  towns  there  should  always  be  a  complete 
organization  for  street-cleaning ;  dust,  mud,  and 
filth  must  be  removed  for  the  health  and  comfort 
of  all  citizens,  tax-payers  or  not. 

Dry  east  winds  do  not  only  arrest  the  action  of 
the  liver,  but  the  parched  state  of  the  roads  allows 
of  poisonous  dust  being  conveyed  to  the  respiratory 
organs.  "  Wash  and  be  clean  "  applies  to  streets  as 
well  as  to  human  bodies. 


26  NATURAL  ASPHALT. 

The  author,  who  has  lived  most  of  his  life  on  the 
continent  of  Europe,  was,  in  a  recent  visit  to  London, 
walking  up  from  Victoria  Station  to  Westminster 
Abbey  by  Victoria  Street.  During  this  short  walk, 
at  four  points  miserable  crossing-sweepers  impor- 
tuned him  for  making  a  passage  across  a  coating  of 
slimy  mud,  which  in  Paris  would  have  been  cleared 
away  before  8  a.m. ;  but  when  wishing  to  cross  the 
same  roadway  from  the  Abbey  to  Great  George 
Street,  there  was  such  a  sea  of  slush  on  the  spongy 
wood  pavement  that  he  was  compelled  to  carry 
his  twelve-year  old  daughter  across  as  though  it 
were  a  river  ford. 

Later  on  the  author  saw  a  house  in  Trafalgar 
Square,  the  walls  of  which  were  literally  black  as 
soot,  and  was  informed  that  it  was  the  College  of 
Physicians.  Dear  old  London !  the  richest,  and, 
after  New  York  and  Chicago,  the  dirtiest  city  in  the 
civilized  world.  When  will  it  be  kept  like  Paris  ? 

Yet  there  are  able-bodied  paupers  of  both  sexes 
in  the  workhouse,  doing  nothing  for  their  board  and 
lodging,  who  would  make  excellent  sweepers. 
Local  Boards  must  learn  to  vote  money  for  street 
cleaning. 

Durability. — Compressed  asphalt,  subjected  to 
ordinary  wear  and  tear,  will  last  without  complete 
renewal  from  15  to  30  years;  for  instance,  the 
compressed  asphalt  laid  in  Cheapside  in  1870, 
resisted  the  central  traffic  of  London  for  over  17 
years,  without  causing  a  single  day's  stoppage  of 


NATURAL   ASPHALT.  2/ 

traffic;  and  there  are  streets  in  Paris  where  the 
asphalt  is  over  30  years  old. 


Fig.    15.— COMPRESSED  ASPHALT   FROM    PARIS   ROADWAYS. 


Fig.    l6. — COMPRESSED   ASPHALT   FROM    PARIS    ROADS,    REDUCED 
BY  WEAR  FROM   2   INCHES   TO  T9FTHS   INCH. 


The  life  of  an  asphalt  roadway  depends  upon 
the  number  of  vehicles  passing  in  24  hours,  their 


28  NATURAL  ASPHALT. 

weight  and  speed,  the  use  of  brakes  ;  also  upon  the 
amount  of  rainfall,  of  frost,  of  hot  sun. 

Repairs  are  made  in  dry  weather  with  hot 
powder,  and  a  careful  workman  will  not  let  his 
jointing  be  visible. 


Fig.    17. — COMPRESSED   ASPHALT    FROM    PARIS    ROADWAYS, 
REDUCED   BY  WEAR   FROM   2   INCHES  TO  TVTHS    INCH. 

In  persistently  cold,  wet,  foggy  weather,  holes 
can  be  temporarily  stopped  by  liquid  asphalt  in 
two  layers,  but  a  dry  surface  of  concrete  can  be 
obtained  by  spreading  a  thin  layer  of  liquid 
mastic  over  it. 

Malleability. — Asphalt,  particularly  in  its  form  of 
mastic,  is  slightly  elastic,  and  at  ordinary  tempera- 
tures (say  60°  Fahr.)  ductile. 

This  gives  it  the  advantage  over  cement  coatings, 
which   are  non-elastic,   and    therefore    crack    and- 
crumble.       Cement    once    used    is    lost,    whereas 
asphalt  mastic,  like   lead,  can   be  used  over   and 
over  again  by  adding  new  refined  bitumen. 


NATURAL  ASPHALT.  29 

In  Paris,  where  there  are  many  trees  in  the 
public  thoroughfares,  the  roots  often  force  up  the 
footpaths  or  side-walks,  yet  the  asphalt  mastic 
rarely  cracks,  although  it  contains  a  large  propor- 
tion of  grit ;  it  bulges  up  only.  In  a  pure  state, 
and  without  grit,  it  might  be  folded  double  without 
cracking. 

Not  affected  by  Frost. — This  quality  allows  of 
snow  being  removed  from  it  with  ease,  and  there 
ensues  no  perceptible  contraction  or  expansion, 
however  sudden  the  changes  of  temperature  may 
be.  In  this  respect  it  compares  favourably  with 
wood  pavement,  which  swells  up  after  rain,  or  frost 
following  rain,  the  force  of  which  expansion  is 
resistless,  pushing  up  kerbs,  overturning  street 
lamps,  or  in  case  of  the  over-resistance  of  a  party 
wall  buckling  up  on  itself. 

Not  affected  by  Heat. — Its  nature  is  not  altered 
thereby;  it  softens  slightly  under  extreme  day  heat 
(say  1 00°  Fahr.),  but  returns  to  its  original  form  at 
sundown.  It  is  a  non-conductor. 

Vermin. — It  repels  rats  and  mice,  perhaps  by  its 
smell,  but  chiefly  by  clogging  up  their  teeth  :  thus 
in  Paris,  where  there  are  as  many  rats  as  Parisians, 
the  sidewalks  are  undermined,  but  the  gritted 
asphalt  mastic  is  never  gnawed  through,  yet  cement 
is  attacked. 

This    quality     renders    asphalt     excellent     for 


30  NATURAL  ASPHALT. 

stables,  granaries,  stores,  warehouses,  corn-mills, 
breweries,  malting-floors,  distilleries,  dairies,  cheese 
factories,  &c. 

Perfection  is  not  of  this  World. — Asphalt  has,  as 
the  French  say,  "  the  defects  of  its  qualities,"  as 
being  impervious  to  water  ;  condensed  atmospheric 
water  remains  upon  it  instead  of  being  absorbed. 
The  only  remedy  for  this  inconvenience  is  a  coarse 
sponge,  or  an  oakum  swab.  Asphalt  does  not 
hide  damp,  it  discovers  the  enemy  which,  being 
seen,  can  be  grappled  with. 

The  best  tool  for  removing  moisture  from  a  hori- 
zontal asphalted  surface  is  the  invaluable  squeegee. 

It  is  also  well  to  remember  that  asphalt,  like 
indiarubber,  has  no  great  powers  of  resistance  per 
se,  but  is  strong  when  supported  by  solid  founda- 
tions or  defended  outside  by  vertical  masonry. 

Noiselessness. — It  is  of  course  owing  to  the  pre- 
sence of  mineral  bitumen  in  the  limestone  which 
causes  percussion  and  vibration  to  be  absorbed  ; 
also  to  this  peculiar  fact,  that  in  a  compressed 
asphalt  the  roadway  is  always  of  closer  texture 
than  the  underlying  parts.  This  is  just  as  per- 
ceptible in  asphalt  worn  to  less  than  half  its 
original  thickness.  (See  Figs.  15  and  1 6  ante.) 

The  sound  of  the  horses'  hoofs  is  heard  as  a 
sharp  "toc-toc,"  without  vibration  or  resonance, 
warning  the  pedestrian  of  an  approaching  vehicle, 
while  the  rolling  of  the  wheels  is  noiseless,  for  the 


NATURAL  ASPHALT.  31 

wheels  do  not  bump  on  asphalt  as  they  do  on  stone 
or  macadam. 

On  wood  pavements  the  sound  of  the  horses' 
hoof  is  not  heard — a  danger  for  deaf  or  careless 
crossers. 

It  has  been  said  indeed,  that  wood  pavement 
cures  deafness  by  killing  off  the  deaf. 

Agoraphobia. — In  these  modern  times  a  new 
malady  has  arisen.  Agoraphobia  is  the  mental 
suffering  caused  by  street  noises  of  all  kinds,  but 
particularly  the  rumbling  of  heavy  vehicles  on 
granite  setts  or  cobble  pavements. 

In  Paris,  for  the  last  twenty-five  years,  land- 
lords, managers  and  heads  of  schools,  churches, 
theatres,  banks,  as  well  as  private  householders, 
have  clamoured  for  compressed  asphalt  road- 
ways, in  some  cases,  where  the  stone  road  was  new, 
paying  2s.  6d.,  or  say  60  cents,  per  foot  run  for  the 
substitution. 

Since  the  cholera  scare  (1892),  a  large  number  of 
narrow  streets  and  blind  alleys,  and  small  yards 
have  been  asphalted  for  hygienic  reasons. 

The  imitation  of  natural  asphalt  will  be  treated 
further  on. 

It  is  an  old  adage  that  "imitators  always  fall 
short,"  and  when  the  difference  in  price  is  so  slight 
between  the  two  articles,  it  is  not  worth  while  to 
encourage  the  imitation. 

The  only  excuse  for  using  imitations  is  their 
low  first  cost,  and  that  is  false  reasoning,  for  the 


32  NATURAL  ASPHALT. 

increased  cost  of  repair  is  infinitely  greater  than 
would  have  been  the  interest  on  the  additional 
outlay  for  the  real  article,  besides  which,  the  com- 
plete break-up  which  always  ensues,  involves  the 
cost  of  relaying,  after  all  the  annoyance  to  the 
neighbouring  householders  and  shopkeepers  caused 
by  the  repairs. 

Asphalt  Fiasco  in  Paris. — In  1878,  the  City 
of  Paris  let  its  tried  contractor  go,  tempted  by 
the  low  prices  of  a  reckless  bidder,  with  the  result 
than  in  1883,  Paris  asphalted  streets  had  gone  to 
the  dogs,  and  had  to  be  relaid  in  1884,  at  a  cost  of 
6,000,000  francs  (240,0007.)  or  1,200,000  dollars. 

The  contractor,  who  had  deceived  himself  as  well 
as  the  town,  died  in  a  mad-house,  leaving  a  host  of 
creditors  with  zero  for  assets,  who  blamed  the  town 
authorities  for  being  the  indirect  cause  of  their 
losing  their  money,  they  believing  that  a  munici- 
pality only  employed  solvent  and  honourable 
contractors. 

Wood  Pavement.— About  the  year  1840  wood 
was  used  for  roadways,  found  wanting  and  aban- 
doned ;  but  since  about  ten  years  ago,  owing  princi- 
pally to  the  failure  of  bad  asphalt  in  Paris  alluded 
to  above,  it  has  been  largely  used.  When  laid  upon 
a  Portland  cement  concrete  bed,  it  is  certainly  a 
great  improvement  upon  macadam,  indeed,  when 
first  laid  it  is  admirable  ;  but  it  is  not  a  hygienic 
pavement,  because  it  is  porous.  As  animals  have  not 


NATURAL  ASPHALT, 


33 


yet  been  trained  to  use  water-closets  and  urinals 
the  public   highways  are   defiled  with  their  dung 


Fig.  1 8. — WOOD    PAVEMENT   CUT   FROM   PA'RIS   STREETS. 

and  their  urine  ;  these,  as  well  as  other  filth,  are 
absorbed  by  the  wood,  and  ferment  in  its  fibres. 

D 


34  NATURAL  ASPHALT. 

Under  a  hot  sun,  morbid  germs  are  drawn  up 
into  the  atmosphere  and  inhaled  by  the  inhabitants, 
stunting  the  growth  of  children  and  debilitating 
adults. 

The  surface  of  wood  pavement  becomes,  after 
one,  two,  or  three  years,  according  to  traffic,  like  a 


Fig.  19. — PULVERIZED   WOOD    FIBRE    MIXED   WITH    HORSE-DUNG 
AND   OTHER   IMPURITIES,    FROM    WOOD   PAVEMENT. 

worn-out  tooth-brush  (see  Fig.  18,  representing  a 
block  taken  from  a  Paris  street  after  one  year's 
wear). 

The  fibres  from  this  disintegrated  surface,  mixed 
with  horse-dung  and  filth,  are  pounded  and  ground 
up  by  the  traffic  (see  Fig.  19),  and  in  this  form,  on 
a  dry  day,  are  swallowed  by  the  citizens,  or  carried 
home  in  their  hair  and  garments. 

Since  the  introduction  of  wood  pavement  in 
London  and  Paris,  oculists  have  found  inflamma- 
tion of  the  white  of  the  eye  (conjunctivitis)  greatly 
on  the  increase.  Such  a  fact  is  not  astonishing,  as 
dust  from  decayed  wood  pavement  is  poisonous. 


NATURAL  ASPHALT.  35 

Wood  pavement,  to  last,  should  be  kept  always 
wet,  but  wet  wood  has  a  most  lugubrious  appearance. 

In  winter,  when  the  frost  gets  into  it,  the  surface 
becomes  glazed  to  such  an  extent  that  horses 
cannot  move  on  it  without  slipping  ;  it  is  dangerous. 

An  eminent  English  engineer  once  said  of  wood 
pavement  ;  first  year  excellent,  second  year  good, 
third  year  bad,  fourth  year  very  bad,  fifth  year 
take  it  away.  As  before  said,  when  laid  on 
concrete  with  a  certain  slope,  wood  has  its  advan- 
tages, the  joints  give  a  foot-hold  to  the  horses  on 
an  incline,  and  the  water  can  get  away,  but  on  the 
flat,  the  rain  water  which  percolates  down  to  the 
concrete,  but  cannot  penetrate  it,  rots  the  wood  at 
its  base. 

In  New  York,  Berlin,  and  the  City  of  London, 
wood  is  no  longer  used,  but  it  is  employed  in  the 
London  suburbs  and  in  Paris,  in  which  latter 
streets,  the  municipal  authorities  lay  it  themselves 
without  the  intervention  of  a  contractor,  as  do  also 
certain  London  parishes. 

Dr.  J.  B.  Fonssagrives  in  his  excellent  and  most 
interesting  work  '  Hygiene  et  Assainissement  des 
Villes  '*  says  (p.  19),  "  Hygiene  cannot  approve  of 
the  covering  of  a  road  by  a  porous  substance,  apt 
to  become  impregnated  by  organic  matter,  and 
supplying  by  its  own  decomposition  miasmata, 
which,  let  loose  from  such  an  extended  surface, 
cannot  be  disregarded.  /  am  convinced  that  in  a 

*  Paris,  J.  B.  Bailliere  et  fils,  Rue  Hautefeuille. 

D   2 


36  NATURAL  ASPHALT. 

damp  town  entirely  paved  with  wood,  marsh  fever 
would  become  endemic? 

There  is  another  danger,  viz.  that  in  case  of  riots 
the  wood  blocks  smeared  with  petroleum  and  set 
alight,  might  aid  the  criminal  design  of  incendiaries, 
as  in  the  case  of  the  Paris  Commune  in  1871. 

Traction  on  Compressed  AspJialt  Roads. — Many 
dynamometrical  experiments  have  been  made  to 
arrive  at  the  coefficient  of  traction  for  each  kind  of 
road,  and  have  yet  to  be  scientifically  carried  out. 

Evidently,  such  experiments  should  be  made  with 
vehicles  of  the  same  weight  and  diameter  of  wheels, 
same  width  of  tire,  on  same  level,  with  same  condi- 
tions of  temperature  and  dryness,  same  speed, 
horses  shod  the  same  without  calkins  or  toe-pieces  ; 
but  it  may  be  taken  roughly  that  the  traction  on 
asphalt,  say  at  75°  Fahr.,  being  I,  that  of  stone'setts 
will  be  2,  of  rough  granite  and  ordinary  macadam 
3,  on  rough  macadam  5  to  6. 


37 


PART    III. 

MODE  OF  SETTING  OUT  COMPRESSED  ASPHALT 
ROADS. 

THE  first  thing  to  be  considered  is  the  camber, 
which  is  pitched  much  lower  than  for  wood,  stone, 
or  macadam,  because  the  asphalt  surface  being 
smooth,  as  well  as  impervious,  the  water  runs 
away  to  the  gutters  more  easily. 

After  trials  of  many  cambers  during  the  last 
twenty  years,  the  author  concurs  generally  with 
the  following  formula,  drawn  up  by  the  late 
M.  Saint-Ange  Allard,  Chief  Engineer  of  the  City 
of  Paris.  The  figures  are  millimetres,  and  are  thus 
given  because  the  metrical  system  is  now  so  much 
used. 

W2 

R  =  0-012  metre  ^rr^. 

R  =  rise  of  camber,  the  perpendicular  at 

highest  point. 
W=  width  of  roadway. 

Thus,  supposing  a  roadway  to  be  12  metres  or 
13  yards  wide  from  kerb  to  kerb,  the  rise  would  be 
0*157  metre  at  the  centre  or  crown,  or  6^  inches, 
but  as  we  take  off  I  metre  or  3  feet  3  inches  from 


3$  NATURAL  ASPHALT. 

the  kerb  to  form  the  gutter— measuring  from  that 
last  limit,  the  rise  is  nearly  0*109  metre,  or 
4^-  inches. 

The  best  way  to  lay  out  a  12-metre  or  1 3-yard 
wide  road  is  to  take  the  centre,  measuring  from 
inside  the  kerbs,  which  are  presumed  to  be  on 
same  level.  Then  take  a  plank,  say  6  metres  or 
ipj-  feet  long,  i  foot  in  width,  and  say  ij  inches 
thick,  upon  the  side  of  which  trace  the  following 
diagram  : — 


Fig.  IQA.— MODE  OF  SETTING  OUT  CONTOURING-BOARDS. 
N.B. — Vertical  scale  much  exaggerated. 


Let  A  B  C  D  (Fig.  IQA)  be  the  configuration,  A  C 
the  side  of  the  granite  kerb,  which  is  1 2  inches  high, 
and  B  D  the  centre  or  crown  of  the  road  at  the 
highest  point,  where  it  is  divided  thus  into  two 
equal  parts. 

Measure  3  feet  3  inches  (i  metre)  from  the  kerb  to 
form  the  gutter,  which  requires  a  greater  fall,  other- 
wise in  rain  storms,  and  flushing,  the  water  would 
spread  too  far  over  the  road  ;  raise  a  perpendicular 
0*048  m.  or  ij-  inch  high,  then  by  joining  E  and 
F  we  have  the  gutter,  which  is  not  steep  enough 


NATURAL  ASPHALT.  39 

to  cause  cart  and  horses  to  slide  towards  the 
kerb,  but  sufficiently  so  to  keep  the  flushing  water 
from  spreading  and  becoming  too  shallow  to  carry 
away  the  street  rubbish,  when  not  too  bulky,  to  the 
gullies. 

At  the  point  D,  we  trace  the  perpendicular  to 
get  the  rise,  after  deducting  the  width  of  gutter, 
which  gives  o*  157  m.  —  0*048  m.  =  0*109  m.  or 
6£  inches  —  ij  inch  =  4f  inches  is  the  height  of  the 
perpendicular  D  O.  Joining  O  to  F  by  a  hori- 
zontal straight  line  we  obtain  the  subtense  of  the 
curve.  To  obtain  the  intermediate  rise  we"  take 
the  fourth  o*  109  m.  =  2^  inches  at  the  point  H  ; 
at  half  the  distance  from  E  to  D  we  raise  the 
perpendicular  H  I,  where  it  is  prolonged  to  J.  By 
joining  the  points  O  J  and  F  C  as  carefully  and 
regularly  as  possible,  the  camber  of  half  the  road- 
way is  obtained.  One  can  always  get  other  points 
by  making  further  similar  subdivisions,  but  in 
practice  it  is  hardly  necessary. 

Now,  to  get  the  camber  edge  all  that  is 
necessary  is  to  saw  the  plank  according  to  the 
curve  ;  C  O  D  then  comes  away  as  waste. 

In  cases  where  one  kerb  is  higher  than  the  other, 
the  highest  point,  or  watershed,  of  the  roadway  is 
of  course  no  longer  in  the  middle,  but,  propor- 
tionately to  the  difference  between  the  height  of 
the  kerbs,  is  advanced  towards  the  higher  one,  but 
the  formula  is  applied  in  the  same  way. 

In  old  cities  there  are  tortuous  narrow  streets 
where  sometimes  the  left  kerb,  sometimes  the  right 


40  -  NATURAL  ASPHALT. 

one,  is  the  higher,  which  causes  a  good  deal  of 
trouble  in  setting  out.  (Fig.  20  represents  a  road- 
way in  which  one  kerb  is  4  inches  higher  than  the 
other) ;  the  highest  rise  of  the  camber  is  no  longer 


!3   Yards 


.   20. 


23'.  O" 


______________  36'.  O"  _____________________________________ 

Fig.  21. 


the  centre  A.  A  longer  slope  must  be  given  to  the 
side  of  the  inner  kerb,  so  as  to  correct  the  inequality. 
The  rise  would  be  at  B,  from  which  point  the  usual 
fall  of  2  in  a  hundred  would  be  given  to  the  points 
M  and  N,  and  from  thence  to  the  kerb  a  fall  of 
3^  in  a  hundred. 

For  a  cross  road  where  the  kerbs  of  each  street 
are  unequal,  by  drawing  a  straight  line  from  each 
rise  we  obtain  at  their  intersection  the  highest 
point  of  the  cross  road,  from  which  the  usual  fall 
of  2  in  100  must  be  given,  so  that  the  water  may 
run  off  freely. 

.As  cross  ways  have  about  double  wear  and  tear, 
they  should  have  extra  thicknesses  of  concrete  and 


NATURAL  ASPHALT.  41 

asphalt.  It  is  generally  the  engineer  or  surveyor 
who  gives  the  points,  and  the  case  is  one  where  much 
practice  and  experience  does  as  well  as  science. 


18.0" 


24-'.  CL*_ 


Figs.    22,  23,  and  24. — IMPLEMENTS  USED  IN  CONTOURING 

ROADWAYS. 


The  Soil. — After  removing  all  plaster  and  soft 
clay,  the  soil  must  be  well  rammed  to  camber 
and  well  watered  to  indicate  holes  ;  should  any 
holes  be  found  they  should  be  filled  in  with  sound 
material. 

Concrete. — From  1871  to  1878  the  author  was 
greatly  troubled  by  being  compelled  to  work 
with  hydraulic  lime  concretes  which  were  never 
dry,  and  formed  the  opinion  that  only  the  best 
Portland  cement  concrete  could  be  used  with 
safety  for  compressed  asphalt.  Cases  of  failure 
in  laying  stone  setts,  or  wood  blocks,  can  be  put 


42  NATURAL   ASPHALT. 

right  at  the  expense  of  the  labour  ;  but  a  failure  in 
compressed  asphalt  means  a  much  more  serious 
loss,  namely  labour  and  material,  which  latter 
must  be  carted  away,  cleaned,  and  ground  up  for 
mastic.  Relaying  annoys  the  householders,  who 
blame  the  engineer  or  architect  as  well  as  the 
contractor. 

The  best  mode  of  making  concrete  for  asphalt 
roads  is,  to  say  one  part  of  fine-ground  Portland 
cement  of  best  quality  add  three  parts  of  clean  sharp 
river  sand,  and  four  parts  of  clean  pebbles  that  will 
go  through  a  ring  of  2j  inches  diameter,  or  one 
part  of  cement  as  above  to  seven  parts  of  clean  river 
ballast,  mixed  dry,  well  shovelled  together  and 
then  just  sufficient  water  added  to  make  it  moist 
(too  much  water  lets  the  heavy  cement  fall  to  the 
bottom).  This  mixture  is  laid  out  with  a  flat  oblong 
shovel  and  afterwards  levelled  off  with  a  straight- 
edge and  smoothed  off  with  the  flat  shovel  so 
that  the  fluid  part  comes  to  the  top,  and  thus  the 
application  of  a  floating  is  avoided  ;  of  course,  a 
little  mortar  must  be  handy  to  fill  up  any  cavities 
after  passing  the  straight  edge. 

The  old  plan  of  spreading  a  floating  over  the 
concrete  is  injurious,  because  (i)  it  does  not  set  at 
the  same  time  as  the  concrete,  and  (2)  it  gets 
crushed  under  the  blows  of  the  rammers  when  the 
powder  is  laid. 

Some  contractors  increase  the  proportion  of 
flint  pebbles  and  sand.  One  part  cement  to  nine 
of  ballast  is  used  often. 


NATURAL   ASPHALT.  43 

In  very  hot  weather  such  a  concrete  will  be 
ready  in  four  days,  but  in  winter  seven  days  is  not 
too  much.  If  it  is  white  on  the  surface  one  may 
be  sure  it  is  dry. 

Latterly,  concretes  have  been  laid  during  the 
existence  of  20°  Fahr.  of  frost,  by  using  water  heated 
to  85°  Fahr.,  in  every  gallon  of  which  I  Ib.  of 
carbonate  of  soda  has  been  dissolved.  It  is  certain 
that  concrete  made  thus  in  the  depth  of  winter 
is  dry  and  apparently  sound.  The  Portland 
cement  mortar  sets  rapidly,  as  if  it  were  Roman 
cement.  The  action  of  the  soda  seems  to  set 
back  the  freezing-point.  Whether  the  process  is 
absolutely  safe,  only  experience  can  decide. 

Time  of  Laying  Asphalt. — In  Europe  the  best 
time  is  between  the  months  of  May  and  October, 
but  work  often  gets  done  much  later,  provided 
there  be  no  frost  and  snow  or  continuous  wet. 

Hot  Asphalt  Powder. — The  powder  should  be 
heated  from  275°  to  280°  Fahr.,  not  only  to  soften 
its  contained  bitumen,  but  also  to  evaporate  the 
natural  moisture  contained  in  the  crude  rock  or 
powder,  which  may  amount  to  from  I  to  I J  per  cent, 
of  the  weight. 

Great  care  must  be  taken  to  rake  out  all  burnt 
or  charred  lumps,  which  are  inert  matter. 

While  the  powder  is  in  the  carts  it  must  be  well 
covered  with  tarpaulins  of  asbestos,  or  other  cloth, 
and  after  being  transferred  to  the  wheel-barrows 
for  spreading  should  be  covered  with  cocoanut 


44  NATURAL   ASPHALT. 

sacking,  as  soon  as  spread  it  should  be  rammed 
with  the  hot  rammers ;  the  less  heat  lost  by  the 
powder  before  ramming  or  tamping  the  better.  No 
foreign  bodies  should  ever  be  left  in  the  powder  or 
concrete. 

The  powder  along  the  kerbs  must  be  rammed 
with  a  special  oblong  rammer,  which  is  also  used 
for  making  joints,  and  a  12-foot  wooden  straight- 
edge should  be  pressed  close  home  to  prove  that  a 
level  surface  has  been  obtained,  so  that  no  hollows 
for  puddles  can  remain.  Any  bumps  must  be  at 
once  rammed  down  while  the  material  is  still  hot. 

When  the  whole  surface  just  rammed  is  level  it 
must  be  smoothed  with  the  hot  smoothing-irons  so 
as  to  glaze  it  and  leave  no  rough  face  to  hold 
water,  then  a  little  fine  Roman  cement  may  be 
sprinkled  over  and  swept  in  with  a  soft  broom,  and 
the  whole  rolled  with  a  heavy  roller. 

If  the  job  can  be  left  for  three  days  so  much 
the  better,  the  atoms  will  cohere  and  take  their 
permanent  set,  but  in  cities  it  is  difficult  to  get  more 
than  24  hours,  during  which  time,  if  the  weather  be 
hot,  the  new  road  may  be  rolled  with  two-wheel 
carts  or  trumbrels,  first  empty,  then  gradually 
loaded  up  ;  this  will  consolidate  the  asphalt  and 
prevent  wheel-marks  when  the  street  is  thrown 
open  to  traffic,  but  in  cool  or  wet  weather  the  cart 
rolling  is  not  necessary. 

The  following  is  the  composition  of  a  gang  for 
the  laying,  say  of  500  square  yards  in  a  day  of  ten 
hours. 


NATURAL  ASPHALT.  45 

2  men  (first  and  second  foreman)  to  rake  out  the  powder  when 

dropped  from  the  barrows,  and  spread  it  in  a  layer  of  equal 

density. 
2  men  to  make  the  joints  along  the  kerbs  or  drain  openings, 

fire  plugs,  £c. 
12  rammers. 
8  smoothers  or  ironers. 
2  men  to  roll  the  heavy  hand  roller. 
4  men  to  roll  the  wheelbarrows  of  powder  from  the  horse  carts 

to  the  site. 

Supposing  that  a  2-inch  layer  of  compressed 
asphalt  be  ordered,  it  is  well  to  trace  with  a 
chalked  string  two  chalk  lines  along  the  kerb,  the 
upper  one  for  the  loose  powder,  the  lower  one  for 
the  layer  after  full  compression.  Some  asphalt 
powders  are  denser  than  others,  so  it  is  v/ell  to  get 
the  weight  of  say  24  Ibs.  to  the  square  foot. 

The  plate  (see  p.  46)  shows  a  square  100,000 
square  feet  in  extent,  in  which  can  be  observed  the 
operation  of  concrete-making  and  powder-laying. 

If  the  proper  weight  per  square  foot  be  given, 
the  roadway  will  roil  down  level  and  to  a  uniform 
thickness  of  two  inches  under  traffic. 

Footpaths  or  Sidewalks  of  Compressed  Asphalt  are 
often  laid  instead  of  gritted  mastic.  The  light 
colour  is  agreeable  to  the  eye  and  harmonizes  with 
stone  buildings  ;  no  surface  can  be  nicer  or  less 
fatiguing  to  walk  on. 

Gritted  Mastic  Footpaths  or  Sidewalks. — A  slope 
of  i  in  50  from  '  hreshold  to  kerb  is  about  what  is 


Fig>    25.— ASPHALT   OF   THE   SQUARE    IN    FRONT   OF   NOTRE    DAME,    PARIS- 
ioO,000   SQUARE  FEET,   EXECUTED   BY  THE   COMPAGNIE   GENERALE   DES 
ASPHALTES    DE    FRANCE.         CONCRETE    BEING     LAID     SIMULTANEOUSLY 
OPPOSITE  THE   WEST   FRONT  OF  THE  CATHEDRAL. 


NATURAL    ASPHALT. 


47 


necessary  to  let  the  water  run  off,  and  a  fillet  of 
pure  mastic  should  be  laid  alongside  the  thresholds 
where  there  is  any  danger  of  infiltration,  paid  for 
extra. 

A  4-inch  depth  of  Portland  cement  concrete  and 
layer  of  mastic  is  sufficient,  except  for  courtyard 


Fig.  26. 

entrances,  where  6-inch  concrete  and  2-inch  layer 
of  mastic  is  necessary,  the  latter  in  two  layers,  first 
smooth,  second  chequered  or  cross-cut  to  afford  a 
foothold  to  horses. 

As  before  mentioned,  in  case  of  repairs,  gas 
trenches,  &c.,  the  old  materials  can  be  used  over 
again. 

Twenty  minutes  after  laying,  the  surface  can  be 
walked  over ;  it  is  agreeable  to  the  foot,  not  hard 


NATURAL  ASPHALT. 


49 


nor  slippery  like  cement  or  granite  flags,  which  in 
dry  weather  are  slippery,  even  dangerous. 

These  famed  asphalt  promenades  are  like  an 
impermeable  carpet,  only  never  dusty  nor  dirty  if 
regularly  washed  down  and  squeegeed. 

The   broad    Parts    Boulevards   would   lose    half 


Fig.   28. — PORTABLE  FURNACE  AND  BOILER   FOR    TRANS- 
PORTING  HOT   MASTIC. 


their  charm  were  they  laid  in  any  other  material 
than  asphalt ;  it  is  the  cheapest  and  the  best  non- 
absorbent,  smooth  and  safe. 

In  hot  climates,  where  frost  is  not  dreaded,  more 
than  the  usual  proportion  of  40  per  cent,  grit  may 
be  added  to  the  mastic  paste ;  the  gritted  mixture 


UNIVERSITY  ) 

/ 


V      f**.. 


5O  NATURAL   ASPHALT. 

should  be  run   hot,  pressed,  and   rubbed  in  with 
slate  powder  or  fine  sand. 

In   the  large   European  towns — London,   Paris, 
Brussels,   &c. — the    gritted    mastic    is    cooked    in 


Fig.   29.— ASPHALT   MASTIC   KETTLE   WITH   ACCESSORIES. 
MASTIC   CAKES    BEHIND. 


boilers  holding  5  tons,  driven  by  steam-power,  and 
the  hot  material  sent  out  in  heated  portable  boilers 
(Fig.  28)  holding  above  I  ton. 

This  saves  blocking  the  street,  and  the  old 
materials  are  carted  away  by  the  same  vehicle, 
which  has  a  box  for  the  purpose. 


NATURAL  ASPHALT.  5 1 

Asphalt  kettles  are  used  for  work  inaccessible  to 
portable  boilers. 

When  used  on  the  public  roads,  they  are  put 
on  a  layer  of  sand  to  prevent  damage  to  the  road 
from  the  heat  and  cinders. 

A  cake  of  Seyssel  mastic,  weighing  say  56  Ibs., 
will  lay  about  n  square  feet  of  surface,  -fg  inch 
thick,  when  the  grit  and  bitumen  has  been  added. 

First,  the  kettle  being  heated,  and  the  cake 
broken  into  small  pieces  by  blows  from  a  small 
sledge  hammer,  about  one-half  of  the  bitumen  to  be 
used,  say  from  5  to  6  per  cent,  of  the  weight  of  the 
pure  mastic,  is  put  in,  then  when  the  paste  is  made 
by  the  addition  of  the  pieces  of  mastic  to  the  bitu- 
men, the  dry  grit  and  half  the  remainder  of  the 
bitumen  is  added  (one-fourth  of  the  whole),  the 
rest  being  kept  till  the  end  of  the  mixing. 

The  grit  is  laid  on  the  top  of  the  mastic,  and 
allowed  to  sink  in,  and  must  afterwards  be  kept 
constantly  stirred.  A  regular  heat  must  be  kept 
up,  not  less  than  280°  Fahr.  nor  more  than 
360°  Fahr. 

Wood  or  coal  or  even  coke  may  be  used  as  fuel, 
and  the  kettles  kept  clean  by  a  chisel  and  hammer. 
The  bottoms  are  movable,  as  they  wear  out  soon. 
In  spreading  the  mastic,  there  must  be  no  steam 
bubbles,  which  arise  from  wet  concrete. 

Fine  sand  dries  a  wet  concrete,  and  during  wet 
weather,  if  spreading  is  compulsory,  the  mastic 
should  not  be  too  hot. 

There  must  be  no  hollows  where  water  can  lodge. 

E  2 


52  NATURAL  ASPHALT. 

To  get  the  thickness  an  iron  rule  may  be  used,  which 
as  it  lies  on  a  rough  surface  should  be  a  little  less 
thick  than  the  layer  to  be  spread. 

Inexperienced  asphalters  sometimes  manage  to 
make  the  surface-water  run  in  the  wrong  direction, 
for  instance  into  a  house  instead  of  from  it. 

It  must  never  be  forgotten  that  we  are  dealing 
with  an  impermeable  material. 

Mastic  is  ready  to  lay  when  it  does  not  stick  to 
the  wooden  spatula  used  for  spreading,  or  by  the 
workman's  test,  when  it  instantly  evaporates 
spittle. 

For  Coatings  of  Masonry. — Mastic  should  be 
used  pure,  and  laid  in  two  layers,  each  about  J  inch 
thick,  taking  care  to  cover  the  first  joints — i.  e. 
that  the  joints  of  the  two  layers  may  not  be  directly 
superposed. 

A  recess  cut  in  the  masonry  and  filled  with 
mastic  is  an  extra  precaution. 

For  Casemates. — Military  engineers  will  some- 
times have  a  brass  rose  and  drain-pipe  inserted  in 
the  mastic  where  several  seams  meet,  so  that  the 
water  may  be  carried  off.  The  rose  is  surrounded 
with  rubble  to  keep  the  dirt  off.  Otherwise  the 
water  remains  underneath  the  bomb-shell  proof 
earth  covering  till  absorbed  by  same. 

When  a  flat  roof  is  asphalted,  as  is  so  often  the 
case  in  countries  where  no  snow  falls,  and  is  used 


NATURAL   ASPHALT. 


53 


as  a  belvedere  or  a  drying  ground,  it  is  well  to  lay 
two  layers  of  mastic — the  first  pure,  the  second 
gritted. 

The  palace  of  the  Trocadero  at  Paris  was  laid 
thus  in  1877,  and  forms  an  excellent  promenade  for 
the  public. 


Fig.  30. 


For  Siloes  (Figs.  3 i,  32). — The  application  here  is 
the  reverse  of  a  casemate,  and  where  green  fodder 
is  earthed  for  winter  use  or  grain  stored.  No 
moisture  from  the  surrounding  earth  nor  any 
vermin  can  get  in. 

Vertical  Applications  are  made  in  pure  asphalt 
mastic  to  keep  out  rising  surface-water  and  dampness 
generally  from  walls  ;  the  material  is  smeared  on 
and  rubbed  in  as  though  it  were  plaster,  and  with 


54 


NATURAL  ASPHALT. 


Fig.  32. 


NATURAL  ASPHALT.  55 

plasterer's  tools.  The  wall  must  not  be  damp  at 
the  time  of  the  application,  and  it  is  well  to  dash 
some  hot  liquid  bitumen  against  the  wall  surface. 
Two  men  are  required,  one  to  spread  and  the  other 
to  briskly  rub  in. 

Such  work  is  worth  nearly  double  the  price  of 
horizontal  spreading. 

It  must  always  be  borne  in  mind  that  asphalt  has 
not  much  power  of  resistance  of  its  own — it  must 
be  supported  by  a  wall  built  up  progressively 
with  the  vertical  application. 

Electricity. — Now  that  underground  wires  are  so 
much  used,  it  has  been  found  difficult  to  obtain  a 
good  conduit ;  cement-concrete  cracks  and  lets  in 
water,  iron  causes  the  current  to  reverse ;  if  the 
wires  are  placed  naked  in  the  earth  there  is  too 
much  leakage. 

The  author  submits  a  plan  with  a  drip-groove 
at  each  end  of  the  lid  (Fig.  13,  ante,  p.  18),  which 
will  be  watertight  and  not  subject  to  crack. 

From  the  wires  that  convey  the  fluid  for  lighting 
purposes  at  the  Paris  Opera  House  (1890),  there 
was  30  per  cent,  leakage,  owing  to  the  condensed 
water  from  the  engine  getting  into  the  covered 
conduits  and  rotting  the  hempen  and  gutta-percha 
coating  off  the  wires. 

As  there  was  no  time  for  making  proper  repairs, 
the  author  rilled  up  the  conduit  with  hot  gritted 
mastic,  drowning  the  wires.  This  was  a  rough  and 
ready  remedy,  but  absolutely  efficacious. 


NATURAL  ASPHALT. 


NATURAL   ASPHALT.  57 

Asphalt  Flags  and  Slabs  (Fig.  33). 

A   is   a    wrought-iron    tank    containing    hot 

water. 
B  is  a  wooden  tray  on  which  the  asphalt  slab 

is  laid  for  immersion. 
C  is  a  stove. 

D,  D,  jointing  irons  with  sharp  edge  for  remov- 
ing overflow. 
E  is  a  ladle  for  melting  the  special  jointing 

mastic — it  fits  on  the  stove. 
F  is  a  wooden  rule  for  proving  level  surface. 
H,  I,  are  slabs,  smooth  and  chequered. 
The  flags  can  be  sent  by  railway  any  distance, 
and  any  intelligentlabourer  can  lay  them  in  towns, 
stables,  out-houses,  schools,  &c. 


58  NATURAL   ASPHALT. 


PART  IV. 

GENERAL  OBSERVATIONS. 

Width  of  Tires — Heavy  Goods  Traffic. — There  is 
a  proportion  between  the  width  of  the  tires  of 
four-wheeled  vehicles  and  the  weight  they  carry  : 
thus— 

Weight  carried  on  four  wheels.  Width  of  Tire. 

2  tons 2  inches  to  2^  inches. 

2j  ,,   to  4  tons 2j    ,,      to  4        „ 

5     »      4      „      to  6        ,, 

7J»      6      „ 

The  diameters  of  wheels  of  course  vary  ac- 
cording to  class  of  goods  carried  and  width  of 
streets. 

If  such  rules  were  carried  out,  roads  would  last 
longer,  but  to  avoid  friction  some  carters  and  van- 
drivers  use  narrow,  rounded  tires,  which  cut  like  a 
knife,  particularly  if  the  gauge  of  the  fore  wheels 
be  the  same  as  the  hind  ones. 

When  a  powerful  lever  brake  is  applied,  locking 
the  two  hind  wheels  and  causing  a  heavy  vehicle  to 
slide  along  in  varying  directions  for  a  distance, 
say,  of  half  a  dozen  yards,  the  road  suffers  ;  the  trace 
left  by  the  wheel  is  hot. 

Spreading  Salt  on  Roads  in  Snowy  Weather. — 


NATURAL  ASPHALT.  59 

This  is  a  deplorable  practice,  snow  and  salt  make,  a 
freezing  mixture  some  28°  Fahr.  lower  in  tempera- 
ture than  the  air. 

This  mixture  runs  down  into  cracks  and  joints, 
and  causes  disturbance  by  the  expansion  of  any 
wet  substance  with  which  it  may  come  in  contact 
during  the  congelation  of  the  other. 

It  does  great  harm  to  shoe  leather,  and  chills  the 
life  out  of  many  an  unsuspecting  wayfarer. 

The  suffering  to  dogs  who  may  wade  in  the 
mixture  is  pitiable. 

The  medical  profession  have  declared  against  it. 
It  certainly  melts  the  snow  on  tram-rails.  It  de- 
prives frozen-out  workmen  of  the  job  of  clearing 
away  snow — a  valuable  resource  for  them. 

Kerbs  should  be  laid  on  a  concrete  foundation 
and  be  12  inches  wide  and  of  a  proportional  depth. 
Grey  granite  is  the  most  sightly  material,  but  it 
requires  facing  with  wrought  iron  at  corners  of 
streets  where  there  is  heavy  traffic. 

Where  water  lies  on  the  concrete  near  the  kerbs, 
the  author  has  inserted  small  iron  drain  pipes 
J  inch  in  diameter.  A  film  of  water  in  a  crack 
will  act  like  a  wedge  under  heavy  traffic. 

Speed  of  Street  Traffic. — From  the  experience 
of  horse  dealers,  the  pace  of  draught  horses  has 
increased  above  25  per  cent,  since  1872,  which 
of  course  means  more  bumping  and  consequently 
more  wear  and  tear. 


6O  NATURAL   ASPHALT. 

Tramcar  Rails  increase  the  cost  of  mainten- 
ance of  roads,  by  concentrating  the  traffic  on  either 
side  and  augmenting  the  number  of  joints. 

Tramway  companies  in  Paris  have  to  pay  all 
repairs  within  20  inches  distance  of  each  rail  or 
double  rail. 

In  towns  the  track  should  always  have  an  over- 
lapping foundation  of  20  inches  thick  Portland 
cement  concrete,  on  which  the  chairs  should  be  laid 
direct. 

Longitudinal  sleepers  on  ballast  are  a  mistake  in 
towns. 

Contracts  for  the  Maintenance  of  AspJialt  Roads 
and  Sidewalks  require  to  be  made  on  a  fair  basis, 
to  avoid  law-suits,  oppression,  fraud  and  bank- 
ruptcy. 

To  take  an  example,  a  householder  buys  a 
carpet.  He  of  course  also  pays  for  laying  it  down, 
keeping  it  clean,  beating  it,  repairing  the  holes 
which  will  appear  in  course  of  time,  and  finally 
when  worn  out  he  buys  and  pays  for  another  one, 
getting  for  the  old  one  what  he  can.  A  munici- 
pality must  do  the  same  for  its  roads  and  foot- 
paths, or  sidewalks. 

Conversion  of  Old  Road  Surfaces  into  Compressed 
Asphalt. — Supposing  a  roadway  in  old  stone  setts  or 
cobbles,  in  macadam  or  wood,  is  to  be  converted 
into  a  roadway  of  compressed  asphalt.  The  first 
thing  is  to  be  sure  that  the  drain  is  made  ;  then  to 


NATURAL   ASPHALT.  6l 

put  the  gas  pipes,  electric  wires,  &c.,  under  the 
footpaths,*  level  up  the  kerbs  and  put  them  on  a 
Portland  cement  foundation,  cart  away  the  old 
materials  at  the  expense  of  the  parish,  make  the 
communication  with  the  water-closets  and  surface 
water  pipes  with  the  main  drain  at  the  expense  of 
the  householders ;  then  relay  the  footpath  or  side- 
walk, and  after  that,  if  there  be  any  trouble  in  the 
roadway,  it  should  be  well  rammed,  watered,  and  an 
extra  thickness  of  concrete  laid  to  prevent  settle- 
ments, which  will  often  occur  after  three  years  or 
more ;  after  that  the  contractor  levels  the  road, 
lays  the  concrete  under  the  superintendence  of  the 
authorities,  and  in  due  time  lays  the  asphalt  as 
before  stated. 

The  job  must  be  stoutly  barricaded  and  the 
public  kept  off,  to  avoid  accidents  and  let  the  work 
be  expedited.  There  must  be  a  watchman  at  night 
to  keep  the  lamps  alight  and  prevent  accidents. 

Guarantee. — In  Paris  a  road  laid  as  '  above  in 
August  is  taken  over  provisionally  on  the  following 
1st  May,  then,  if  in  good  order,  it  is  passed,  but 
left  in  the  contractor's  hands  at  his  risk  till  the' 
3 ist  December  following;  after  which,  if  still  in 
good  order,  it  is  taken  over  definitively  by  the 
municipality  and  parish  as  their  own  property,  and 
all  repairs  are  at  their  charge. 

*  Unless  there  be  subways,  a  most  valuable  adjunct  to  a  road, 
of  which  Colonel  Haywood,  the  City  of  London  Engineer,  has 
made  many. 


62  NATURAL  ASPHALT. 

Payment. — Sums  on  account  are  paid  upon  the 
engineer's  certificate  as  the  work  progresses,  but  one- 
tenth  is  always  retained  till  the  definitive  reception 
has  taken  place. 

Maintenance  is  of  two  kinds,  1st  that  of  gas  and 
water  and  electricity  trenches,  changes  of  levels, 
widenings,  &c,  which  is  paid  according  to  the 
schedule  of  prices,  with  a  premium  for  surfaces 
from  i  to  100  yards,  also  for  settlements  ;  trenches 
should  always  be  measured  from  the  bottom  not 
the  top,  the  contractor  removes  the  earth  and  old 
materials  at  schedule  prices  ;  (2)  Maintenance  for 
wear  and  tear. 

Now  according  to  the  simile  of  the  house- 
holder's carpet,  the  municipality  or  parish  would 
keep  paying  the  necessary  repairs  as  caused  by 
the  traffic  or  "  wheel  wear,"  until  at  a  given  time  it 
would  have  to  relay  the  entire  asphalt  surface  and 
level  up  the  concrete  bed,  if  there  had  been  many 
trenches,  at  its  own  expense.  Of  course  the  old 
asphalt  has  a  certain  value,  but  it  has  to  be  carted 
to  the  contractor's  yard,  stored,  cleansed,  ground 
up,  all  of  which  means  expense  to  the  contractor, 
who  has  also  to  wait  the  opportunity  of  using  it,  so 
that  it  is  often  given  for  the  cartage  as  its  storage 
on  expensive  land  soon  eats  up  its  value. 

But,  instead  of  paying  for  its  repairs  by  surface 
as  required,  the  town  of  Paris  resolved  to  pay  a 
fixed  sum  per  square  measure  of  surface,  a  sum 
based  upon  its  expenses  during  three  years,  leaving 


NATURAL  ASPHALT.  63 

all  the  rest  to  the  contractor,  who  is  at  the  beck 
and  call  of  its  engineers,  for  all  necessary  repairs, 
whatever  they  may  be  in  extent,  which  is  an  easy 
method  in  a  large  city,  and  causes  a  large  saving  in 
figures  and  red  tape. 

This  sum  is  2  francs  per  square  meter,  or  say 
is.  ^d.  or  32  cents  per  square  yard  for  compressed 
asphalt  roadways,  and  35  centimes  per  square  meter, 
say  ^d.  or  6  cents  per  square  yard  for  gritted 
asphalt  footpaths  or  sidewalks. 

The  contract  is  made  for  ten  years,  and  at  the 
end  of  that  time  the  surface  must  be  in  good  order, 
but  of  the  thickness  no  note  is  taken. 

It  may  happen  under  such  a  contract  that  the 
contractor  may  lose  money  upon  the  maintenance 
of  certain  streets,  but  others  will  give  him  a  profit 
and  so  compensate. 

Of  course  under  such  a  system  the  contractor  is 
not  supposed  to  lose,  still  he  often  does,  owing  to 
prolonged  bad  weather,  unusual  traffic,  bad  con- 
crete, &c.,  so  that  it  is  usual  to  give  him  all  new  work 
up  to  3OOO/.  or  1 5,000  dollars,  without  rebate. 

The  system  of  paying  a  fixed  price  for  repairs 
of  whatever  extent  is  a  risk  for  the  contractors,  and 
if  undue  severity  is  exercised  by  the  authorities 
may  lead  to  his  ruin,  but  it  is  never  the  interest  of 
a  municipality  to  punish  an  honourable  contractor. 
Still,  coercive  means  are  reserved  for  dishonourable 
contractors,  and  caution  money  is  required  for 
large  contracts  which  may  rise  to  I2,ooo/.  or  60,000 
dollars,  bearing  3  per  cent,  interest. 


64  NATURAL  ASPHALT. 

The  city  of  Berlin  requires  a  5  years'  guarantee, 
and  pays  maintenance  for  15  years  afterwards. 
Caution  money  is  required,  for  which  4  per  cent,  is 
paid ;  but  the  traffic  of  Berlin  is  easy  compared  to 
that  of  London,  and  above  all  to  that  of  Paris, 
which  is  the  heaviest  known. 

The  city  of  New  York  requires  a  5  years' 
guarantee  for  some  work  and  a  15  years'  guarantee 
for  other,  maintenance  of  which  must  be  included 
in  the  bid  for  the  whole  time. 

New  York  does  not  vote  annual  sums  for  main- 
tenance as  other  towns  do,  and  instead  of  caution 
money  requires  bondsmen  ;  two-thirds  of  the  money 
is  paid  down  and  the  other  third  paid  in  small 
sums  until  the  guarantee  is  expired. 

The  system  is  not  so  good  as  that  of  Paris  or  of 
London  (which  latter  is  nearly  the  same  as  that  of 
Paris),  or  of  Berlin,  because  contractors  cannot 
calculate  how  much  the  wear  and  tear  of  a  big 
town  increases.  It  is  certain  that  many  streets  at 
the  end  of  ten  years  will  have  cost  as  much  to 
repair  as  was  paid  for  the  asphalt,  including  con- 
crete, when  laid. 

One  well-known  contractor  in  New  York  has 
preferred  (1892)  to  abandon  say  142,000  dollars 
owing  to  him  by  the  municipality  rather  than  con- 
tinue repairs,  which  at  the  end  of  1 5  years  will  have 
cost  three  times  that  sum  or  more. 

The  only  one  who  can  gain  by  this  is  the  out- 
side contractor  called  in  to  do  repairs  as  long  as  the 
funds  last. 


NATURAL  ASPHALT.  65 

The  city  of  London  requires  two  years'  guarantee 
for  new  work,  after  which  it  pays  a  fixed  sum  for 
maintenance  per  square  yard  during  15  years, 
according  to  the  traffic  of  the  street. 

Thus,  Cheapside,  London — 2j-inch  compressed 
asphalt  on  9-inch  Portland  cement  concrete — was 
paid  iSs.  or  4*32  dollars  per  square  yard,  and,  the 
guarantee  time  expired,  is.  6d.  or  36  cents  mainte- 
nance per  square  yard  during  15  years.* 

The  author  has  been  informed  that  Cheapside, 
which  was  and  is  a  marvel  of  endurance,  was  a  loss 
to  the  contractors  in  the  latter  years  before  it  was 
relaid. 

During  the  whole  of  the  17  years  this  important 
thoroughfare  was  never  stopped  for  repairs,  i.e.  from 
1870  to  the  end  of  1887,  although  when  the  old 
granite  setts  were  used,  it  had  to  be  relaid  every 
4  years. 

It  was  relaid  at  the  rate  of  800  square  yards  a 
day  with  comparatively  little  inconvenience  to  the 
public. 

Low  Prices. — It  is  not  well  for  a  contractor's  prices 
to  be  cut  too  low  ;  experience  has  shown  that  very 
low  prices  mean  one  of  two  things,  either  ruin  to  the 
contractor,  which  is  a  public  misfortune  of  frequent 

*  See  the  report  of  Colonel  Haywood,  Engineer  and  Surveyor  to 
the  City  of  London,  Engineer's  Office,  Guildhall,  London.  It 
was  this  distinguished  engineer  who  introduced  compressed 
asphalt  into  London,  in  1869 — a  boon  indeed  for  those  old  narrow 
streets  and  alleys. 

F 


66  NATURAL  ASPHALT. 

occurrence,  or  else  cheating,  i.  e.  substitution  of 
second  class  materials,  insufficient  thicknesses, 
&c.,  when  the  town  suffers  —  sometimes  found 
out  too  late.  Fraud  is  always  more  active  than 
supervision. 

Poor  human  nature  must  not  be  tempted  too  far. 
High  duties  produce  smuggling;  excessive  income 
tax  leads  to  false  returns  of  income  ;  very  low 
prices  in  contracting  lead  to  cheating. 

Municipalities  should  encourage  honourable  con- 
tractors who  do  good  work,  by  only  allowing  those 
contractors  to  compete  for  important  jobs  who 
have  capital,  plant,  good  materials,  and  an  un- 
blemished reputation. 

A  needy,  incompetent  and  dishonest  contractor 
does  infinite  harm  to  those  who  trust  him,  whilst 
doing  no  good  to  himself. 

Imitations  of  Natural  Asphalt. — These  are  of 
two  classes,  the  first  and  foremost  is  a  material 
made  of  white  limestone  sand,  and  Trinidad  or 
other  mineral  pitch. 

Trinidad  pitch  always  contains  25  per  cent,  of 
clay,  whereas  the  bitumen  or  pitch  naturally  con- 
tained in  asphalt  rock  is  chemically  pure. 

Bitumen  can  be  added  to  natural  asphalt,  be- 
cause nature  has  shown  the  way. 

If  you  have  an  oil  stain  in  a  piece  of  cloth, 
and  pour  fresh  oil  on,  it  will  soak  into  the  part 
already  stained  much  more  readily  than  into  the 
part  still  intact. 


NATURAL   ASPHALT.  67 

The  fact  is,  that  it  is  about  as  easy  to  imitate 
natural  asphalt  as  to  imitate  granite  or  coals. 

There  is  no  chemist  like  nature.  However,  in 
the  United  States,  a  man  of  great  natural  gifts  and 
extraordinary  energy,  Mr.  Barber,  has  founded  a 
powerful  company  for  making  roadways  of  the 
Trinidad  pitch  compound  above  alluded  to. 

Of  this  artificial  compound,  more  than  5,000,000 
square  yards  have  been  laid  in  various  towns  of 
the  great  continent.  It  resists  well  enough  where 
there  is  little  traffic,  but  tried  in  Paris,  Berlin,  and 
the  heavy  traffic  streets  of  New  York,  like  Wall 
Street  and  Chambers  Street,  it  scales  away  at  the 
surface  and  breaks  up  rapidly. 

Mr.  Barber  is  preparing  the  way  for  a  better  pave- 
ment, i.e.  compressed  natural  asphalt.  In  America, 
as  elsewhere,  the  best  article  always  comes  to  the 
front  in  the  end,  and  the  best  is  always  the  cheapest 
in  the  long  run. 

Some  engineers  will  argue  that  it  is  well  to  use 
a  cheap  though  inferior  material  for  streets  with 
little  traffic. 

The  author,  however,  would  venture  to  assert 
that  it  is  always  advantageous  to  use  the  best 
material,  and  arrive  at  lower  prices  by  modify- 
ing the  thicknesses  of  the  concrete  and  asphalt 
layer. 

Yet  in  Berlin  the  town  engineers  have  always 
laid  8-inch  Portland  cement  concrete,  and  2-inch 
asphalt,  and  probably  in  the  end  their  plan  is  most 
economic,  as  streets  with  small  traffic  often  become 


68  NATURAL  ASPHALT. 

streets  with  heavy  traffic  in  the  course  of  20  years, 
say. 

In  London,  during  the  year  1871,  many  imitation 
asphalts  were  tried — such  anomalies  as  "iron  as- 
phalt," "  india-rubber  asphalt,"  "  granite  asphalt," 
"  slate  asphalt."  They  have  all  disappeared — only 
the  real  article  remains. 

In  Paris,  about  1880,  a  plan  of  sprinkling  asphalt 
powder  with  collodion  to  soften  the  bitumen  was 
tried,  instead  of  heating,  the  object  being  to  allow 
of  repairs  being  done  in  wet  weather  without 
vaporising  the  water,  as  the  hot  asphalt  powder 
does,  thus  causing  nodulous  formation  in  the  com- 
pressed layer. 

The  inventor  had  used  collodion  for  moistening 
gunpowder,  and  of  so  obtaining  a  greater  com- 
pression in  the  cartridge,  but  he  forgot  that 
heating  was  necessary,  not  only  for  softening 
the  bitumen,  but  also  for  chasing  away  the  i£ 
per  cent,  of  water  contained  in  the  natural  rock, 
and  which,  if  left  in,  would  cause  breaking  up  in 
frosty  weather. 

This  so-called  cold  asphalt  has  long  disappeared 
from  the  streets  of  Paris. 

The  second  imitation  of  natural  asphalt  is  made 
by  using  shale-oil,  or  petroleum-still  bottoms, 
instead  of  Trinidad,  and  mixing  sand  with  lime- 
stone. This  compound  goes  soft  in  summer,  and 
has  little  power  of  resistance. 

The  third  and  most  redoubtable  imitation  is  that 
in  which  gas-tar  is  used  instead  of  bitumen,  on 


NATURAL  ASPHALT.  69 

account  of  its  cheapness.     Mastic  made  with  gas 
tar,  is  soft  in  summer  and  brittle  in  winter. 

When  used  under  its  own  name  of  gas-tar  mastic, 
nothing  can  be  said  ;  unfortunately,  having  nearly 
the  same  colour  as  natural  asphalt  mastic,  it  gets 
palmed  off  as  the  real  article,  although  the  ap- 
pearance, the  fracture-colour  and  smell  are  not  the 
same.  That  does  harm,  as  the  engineer  and 
architect,  once  deceived  by  an  unprincipled  con- 
tractor, may  afterwards  taboo  real  asphalt,  and 
prefer  to  it  cement,  tiles,  bricks,  &c. 

Gas-tar  mastic  can  be  detected  otherwise  than 
by  the  result  it  gives — ist,  by  its  acrid  odour ;  2nd, 
its  metallic  sound  when  cold,  its  fluidity  when  hot. 

Gas-tar  contains  the  aniline  dyes,  which  are  not 
found  in  mineral  pitch. 

It  would  be  better  for  gas-tar  to  be  used  for  its 
chemical  derivatives,  or  for  agglutinating  coal-dust 
(compressed  fuel),  than  for  making  imitation  as- 
phalt, which  is  not  trustworthy,  even  when  free 
from  atmospheric  influences. 

Traffic  of  Paris. — Asphalt  streets  laid  by  the 
Compagnie  Generale  des  Asphaltes  de  France,  the 
originators  of  the  system  :— 


RuedeRivoH  .. 

Rue  Croix  des  Petits  Champs  do.  20,480 

Rue  St.  Honore        do.  19,672 

Rue  Auber do.  14,082 

Avenue  de  la  Grande  Arrnee  ..  do.  8, 149 


70  NATURAL  ASPHALT. 

Whereas  the  highest  traffic  in  London  for  as- 
phalted streets  is — 


King  William  Street 

("number  of  vehicles) 
\passing  in  24  hours/ 

26,793 

Gracechurch  Street.. 

do. 

15,585 

Queen  Victoria  Street 

do. 

i6,53i 

Cheapside    .      .. 

do 

i  5  ,  206 

Aldgate      

do. 

14,200 

Holborn  Viaduct 

do. 

12,158 

Newgate  Street 

do. 

13,128 

Moorgate  Street 

do. 

n,398 

Cornhill      

do. 

9,572 

These  figures  are  taken  from  a  report  by 
M.  Barabant,  late  chief  engineer  of  the  city 
of  Paris,  now  general  manager  of  the  Eastern 
Railway  Company  of  France.* 

Macadam. — The  wear  and  tear  of  macadamised 
roads  in  Paris,  the  extent  of  which  is,  say  2,167,800 
square  yards,  or  -f^  of  the  entire  surface  of  Paris 
roadways,f  absorbs  daily  390  cubic  yards  of 
materials  or  a  train-load  of  thirty- six  waggons.}: 

Where  does  the  detritus  of  this  immense  daily 
cube  of  broken  stone  go  ?  Into  the  respiratory 
organs  of  the  Parisians,  their  hair,  clothes,  houses ; 
into  the  street  gutters,  thence  to  the  drains,  and 

*  '  Note  sur  les  questions  de  viabilite,  par  M.  Barabant,  Ingenieur 
en  chef  de  la  voie  publique.'  Chaix,  29  Rue  Bergere,  Paris. 

t  '  Note  sur  1'entretien  des  voies  publiques  de  Paris,  par  M. 
Allard.'  1 1  Rue  Cadet,  Paris. 

J  '  Variations  de  la  circulation  dans  les  rues  de  Paris  de  1872  a 
1887,  par  M.  Andre,  Ingenieur  en  chef.'  17  Rue  Cadet,  Paris. 


NATURAL  ASPHALT.  71 

thence  again  to  the  river  Seine,  to  form  therein 
banks  of  silt  and  mud,  which  must  be  dredged 
away  or  navigation  would  eventually  be  stopped. 
No  wonder  that  its  suppression  is  desired.  Its 
cost  is  terrible ;  the  maintenance  of  a  crowded 
thoroughfare  being  half  the  cost  of  laying  a  new 
asphalt  road,  including  the  concrete  foundation. 

Work  done  by  Parishes  and  Municipalities  without 
the  Intermediary  of  Contractors. — It  may  be  laid 
down,  that  work  done  by  the  parish  or  municipality 
is  in  the  end  always  dearer  than  that  done  by 
honourable  contractors,  although  by  the  way  of 
stating  the  case,  it  may  appear  at  first  sight 
cheaper.  A  parish  has  the  inherent  right  to  do 
its  own  work,  be  its  own  contractor  in  fact,  only  it 
certainly  should  not  compete  with  the  contractor 
for  public  and  private  work. 

In  Paris  the  city  lays  its  own  wood,  rolls  its 
own  macadam,  does  its  own  paving  repairs,  though 
not  those  for  kerbs,  does  its  street-cleaning,  but 
not  the  carting  away  of  dung,  detritus,  rubbish,  and 
snow. 

The  parish  or  municipality  pays  no  rates  and 
taxes,  buys  its  raw  material  as  cheap  as  the  con- 
tractor, uses  its  engineers  and  staff  engaged  for 
control  without  extra  payment,  but  it  is  hampered 
by  the  system  of  accounts,  has  to  pay  its  staff  at 
the  depots,  the  rent  of  same,  and  interest  on  cost 
of  machinery  plus  repairs,  whether  work  is  going 
on  or  not,  and  in  case  of  failure  has  no  one  to  hold 


72  NATURAL  ASPHALT. 

responsible.  The  result  is  invariable — work  is  slow, 
labour  dear  and  inefficient. 

It  is  a  well  known  fact  in  Paris  that  the  con- 
tractor gets  three  times  more  work  out  of  his  men 
than  a  parish ;  he  has  picked  men  and  pays  them 
proportionately.  Then  supposing  wood  pavement 
laid  in  Paris  by  the  town  staff  to  cost  apparently 
20  per  cent,  less  than  the  contractor's  price  ;  the 
maintenance  in  any  case  will  cost  three  and  a  half 
times  as  much. 

It  is,  however,  probable  that  if  instead  of  making 
an  estimate  of  the  first  cost,  the  actual  figures  were 
taken — rent,  taxes,  loss  of  time  owing  to  lack  of 
materials  (a  frequent  case),  and  a  fair  apportion- 
ment of  engineer's  salary  and  that  of  the  staff,  the 
cost  would  be  20  per  cent,  more. 

It  seems  only  fair  that  if  a  parish  exacts  poor- 
rates  and  taxes  from  contractors,  it  should  not 
deprive  them  of  the  means  of  earning  something. 

Cost  of  Work  in  Paris. — Paris  being  the  town 
in  which  the  asphalt  trade  took  its  rise,  the  author 
thinks  it  well  to  give  the  prices  paid  there,  of 
course  premising  that  in  other  countries  there  is 
additional  carriage  from  the  mines,  and  sometimes 
custom  duties,  as  in  Amercia,  Canada,  and  Austria, 
on  the  manufactured  material,  but  not  the  raw 
rock. 

Wage  of  an  asphalter,  per  hour    ..      ..  *]\d.  or  15  cents, 

help  , 5fc/.  „  n      „ 


NATURAL   ASPHALT. 


73 


Portland  cement  concrete,  6  in.  thick.. 

,,  ,,  8        „        .. 

Liquid  asphalt  mastic  gritted,  £  in.  thick 

„  pure,  no  grit,  T9g       ,, 

,,  when  laid  vertically       .. 

Natural  compressed  asphalt,  2  in.  thick 

For  jobs  up  to  10  yards  on  surface       .. 

,,       of  I  o  to  20  yards  on  surface 
Fillets  extra,  canvass  or  paper  when  spreading  on  wood,  extra. 
Grey  granite  kerbs,   12  inches  by   12   inches,  on  concrete  and 
jointed  complete,  13^.  2.d.  or  3*64  dollars  the  running  yard. 


Per  square  yard. 
$s.  %d.  or    88  cents. 
4^.  %d.  „  i'i2    dollars 
qs.  2d.  ,,  I  *co      ,, 
4.5-.  2d.  „  I'oo      ,, 
$s.  6d.  ,,  1*32       ,, 
gs.  2d.  ,,  2*20       ,, 
20  per  cent,  cubic. 
10  ,, 


Old  gritted  mastic,  old  pure  mastic,  old   com- 
pressed, are  taken  back  by  special  arrangements. 


Chicago  World's  Fair,  1893.  —  Specimens  of  all 
the  natural  substances  described  in  foregoing  pages 
will  be  found  in  Class  12,  Mines;  and  the  author 
will  be  happy  to  receive  any  correction  or  notice 
in  view  of  a  second  edition  later 


LONDON:  PRINTED  BY  WILLIAM  CLOWES  AND  SONS,  LIMITED, 
STAMFORD  STKEET  AND  CHARING  CROSS. 


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.JAN  2b  1941 

"50 

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